Wear-out monitor device

ABSTRACT

The disclosed technology generally relates to integrated circuit devices with wear out monitoring capability. An integrated circuit device includes a wear-out monitor device configured to record an indication of wear-out of a core circuit separated from the wear-out monitor device, wherein the indication is associated with localized diffusion of a diffusant within the wear-out monitor device in response to a wear-out stress that causes the wear-out of the core circuit.

INCORPORATION BY REFERENCE

This application claims the benefit of priority of and incorporates byreference the entirety of each of the following provisional patentapplications: U.S. Provisional Application No. 62/324,828, filed Apr.19, 2016; U.S. Provisional Application No. 62/447,824, filed Jan. 18,2017; and U.S. Provisional Application No. 62/455,481, filed Feb. 6,2017. This application is a continuation-in-part of U.S. applicationSer. No. 15/291,742, filed Oct. 12, 2016, the entire disclosure of whichis hereby incorporated by reference in its entirety herein.

FIELD OF THE DISCLOSURE

The disclosed technology generally relates to wear-out monitor devicesfor integrated circuit devices.

BACKGROUND

Mission lifetimes of some integrated circuit (IC) devices can bepredicted based on, e.g., theoretical, empirical or semi-empiricalmodels of failure mechanisms. Failure mechanisms, in turn, depend on thetype(s) of wear-out stress(es) that cause failure of the IC devices.Stresses that cause wear-out of the IC devices include thermal stress,voltage (or electromagnetic field) stress, current stress, andmechanical stress, among other types of stresses. Some failures arecaused by acute stresses, e.g., an electrical overstress (EOS) or anelectrostatic discharge (ESD) event, while other failures are caused bycumulative stresses, e.g., thermal, voltage or current stresses duringoperation. The IC devices that are subjected to these wear-out stressesbeyond their predicted mission lifetimes can be subject to increasedprobability of reliability failures, which can be sudden andcatastrophic. For example, certain thermally activated failuremechanisms, e.g., data retention of memory devices, have predictabletime-to-fail at a given temperature. However, the stresses that causewear-out can be intermittent and variable. As a result, it can bedifficult to predict a time-to-fail even when the failure mechanisms arerelatively well-known. Therefore, it is desirable to monitor cumulativestresses real-time, such that a user can monitor, e.g., automatically,how close to the end of the mission lifetime the IC device actually is,to avoid sudden failures.

One approach to monitor wear-out stresses may be to implement a sensorsystem. The sensor system can include one or more sensors, e.g., atemperature sensor and a current sensor, for measuring the stresses andthe associated circuitry for converting the measured stresses. Themeasured values associated with the stresses can then be recorded andtracked for possible excursions outside a prescribed limit. Suchmonitoring can be performed over a lifetime of a product to alert theuser of a predicted failure. However, there can be a number ofrestrictions for such a system. For example, the sensor system mayinclude a power supply for continuous sensing over the lifetime of theproduct. In addition, the sensed signal, e.g., voltage or currentsignal, may be volatile and be lost if not stored. A wear-out level of acomponent being monitored may then be calculated from the storedinformation. As a result, a built-in memory and/or an ability totransmit information to an external memory may be implemented.Furthermore, the range of monitored conditions may be limited by thesensors themselves. For example, if the sensor is a semiconductor-baseddevice, the range of temperature, voltage and/or current that can bemonitored for the monitored component may be limited by the operatingparameters of the semiconductor-based device. Outside of the range,excursions may not be monitored and recorded because of possiblefailures of the sensor system itself. Thus, there is a desire forimproved wear-out monitor devices.

SUMMARY OF SOME ASPECTS OF THE DISCLOSURE

The innovations described in the claims each have several aspects, nosingle one of which is solely responsible for its desirable attributes.Without limiting the scope of the claims, some prominent features ofthis disclosure will now be briefly described.

In one aspect, an integrated circuit device with wear out monitoringincludes a core circuit and a wear-out monitor device. The wear-outmonitor device is configured to adjust an indication of wear out of thecore circuit regardless of whether the core circuit is activated. Theintegrated circuit device additionally includes a sensing circuitconfigured to detect an electrical property associated with the wear-outmonitor device, wherein the electrical property is indicative of thewear out of the core circuit.

In some embodiments, the wear-out monitor device comprises a substrateand monitor atoms configured to diffuse in the substrate, wherein adoping profile of the monitor atoms in the substrate is indicative ofwear out of the core circuit.

In some embodiments, the monitor atoms have a diffusion activationenergy between 0.75 eV and 2.5 eV in the substrate.

In some embodiments, the monitor atoms includes one or more elementsselected from the group consisting of aluminum (Al), cobalt (Co),platinum (Pt), sulfur (S), nickel (Ni), silver (Ag), zinc (Zn), gold(Au), chromium (Cr), copper (Cu), iron (Fe), sodium (Na), and potassium(K).

In some embodiments, the core circuit and the wear-out monitor deviceare formed in the substrate that is a common substrate formed of asemiconductor material and configured such that the monitor atoms remainin the wear-out monitor device under a wear-out stress without diffusinginto the core circuit.

In some embodiments, the wear-out monitor device includes a reservoir ofthe monitor atoms formed on a surface of the substrate, wherein thereservoir serves as a first electrode of the wear-out monitor device,and wherein the wear-out monitor device further comprises a secondelectrode on the surface formed of a different material than the firstelectrode.

In some embodiments, the substrate includes a semiconductor material asa diffusing medium for the monitor atoms.

In some embodiments, the monitor device includes a PN junction, whereinthe reservoir physically contacts one of a p-doped region or an n-dopedregion of the PN junction, and wherein the second electrode electricallycontacts the other of the p-doped region or the n-doped region.

In some embodiments, the electrical property includes a reverse biascurrent of the PN junction.

In some embodiments, the monitor device comprises a first doped regionand a second doped region that are separated from each other andconfigured to punch-through under a bias between the first doped regionand the second doped region, wherein the first doped region and thesecond doped region have opposite conductivity types, and wherein themonitor atoms are configured to diffuse from the first doped regiontowards the second doped region under the bias.

In some embodiments, the second doped region is a buried region that isvertically separated from the first doped region that is formed at asurface of the semiconductor material.

In some embodiments, the first doped region and the second doped regionare formed at a surface region of the semiconductor material and arelaterally separated from each other.

In some embodiments, the monitor device includes a field effecttransistor comprising a source region and a drain region that areseparated from each other by a channel region, and wherein, under abias, the monitor atoms are configured to diffuse from one of the sourceregion or the drain region into the channel towards the other of thesource region or the drain region.

In some embodiments, the integrated circuit device further includes areference device coupled to the sensing circuit, wherein the sensingcircuit is configured to provide an indication of wear-out based on acomparison of the electrical property of the wear-out monitor devicewith a corresponding electrical property of the reference device.

In some embodiments, the reference device includes the same type ofdevice as the wear-out monitor device while having at least oneelectrode formed of a material different than a corresponding electrodeof the wear-out monitor device having the monitor atoms.

In some embodiments, the indication of wear-out is indicative of one ormore of a thermal stress, a voltage stress, or a current stress.

In some embodiments, the monitor atoms are configured such that awear-out stress causes a change in a rate at which the monitor atomsdiffuse in the substrate.

In some embodiments, the wear-out monitor device includes a p-dopedregion and an n-doped region, wherein the p-doped region comprises ap-type dopant different from the diffusing material and the n-dopedregion comprises an n-type dopant different from the diffusing material.

In another aspect, a method of monitoring a wear-out of an integratedcircuit device including a core circuit and a wear-out monitor deviceincludes detecting an electrical property of a wear-out monitor device,wherein the wear-out monitor device includes a semiconductor materialand monitor atoms configured to diffuse into the semiconductor material,and wherein the electrical property corresponds to a concentrationprofile of the monitor atoms in the semiconductor material that isindicative of wear-out of the core circuit. The method additionallyincludes reporting the electrical property of the wear-out monitordevice.

In some embodiments, prior to detecting, the method includes subjectingthe integrated circuit device to a stress condition that causes themonitor atoms diffuse in the semiconductor material.

In some embodiments, the method further includes determining whether thewear-out of the core circuit has reached a predetermined level based onthe detected electrical property of the wear-out device.

In some embodiments, the monitor device comprises a plurality of dopedregions and a reservoir of the monitor atoms physically contacting oneof the doped regions and serving as an electrode, and detecting theelectrical property includes measuring a current or a voltage using theelectrode.

In some embodiments, the stress condition comprises one or more of athermal stress condition, a voltage stress condition, or a currentstress condition.

In another aspect, an integrated circuit device with wear-out monitoringincludes a core circuit and means for recording wear-out of the corecircuit as a doping profile of a diffusing material in a substrate. Theintegrated circuit device additionally includes means for detecting anindication of wear-out of the core circuit, the means for recordingwear-out being in communication with the means for recording theindication of wear-out.

In some embodiments, the diffusing material has a diffusion activationenergy in the substrate between 0.75 eV and 2.5 eV.

In some embodiments, the substrate is a semiconductor substrate.

In some embodiments, the means for recording includes a first dopedregion doped with a first dopant of a first type and a second dopedregion doped region doped with a second dopant of a second type.

In some embodiments, the means for recording further includes areservoir comprising atoms of the diffusing material, wherein thereservoir contacts one of the first doped region or the second dopedregion.

In some embodiments, the means for recording includes a PN junctionhaving a p-doped region and an n-doped region, wherein the p-dopedregion comprises a p-type dopant different from the dopant and then-doped region comprises an n-type dopant different from the diffusingmaterial.

In some embodiments, the means for recording includes ametal-oxide-silicon transistor having a source region and a drainregion, wherein the source region and the drain region are doped with ann-type dopant or a p-type dopant different from the diffusing dopant.

In some embodiments, the means for recording comprises a monitoringregion and a reference region formed in the substrate, wherein each ofthe monitoring region and the reference region comprises the diffusingmaterial and at least the reference region comprises a barrierconfigured to restrict diffusion of the diffusing material into thesubstrate.

In some embodiments, the means for detecting is configured to measureimpedance values from each of the monitoring region and the referenceregion and to determine the wear-out of the core circuit based on acomparison of the measured impedance values.

In another aspect, an integrated circuit device comprises a wear-outmonitor device configured to record an indication of wear-out of a corecircuit separated from the wear-out monitor device, wherein theindication is associated with localized diffusion of a diffusant withinthe wear-out monitor device in response to a wear-out stress that causesthe wear-out of the core circuit.

In some embodiments, the wear-out monitor device comprises a reservoircomprising the diffusant and a diffusion region in communication withthe reservoir, such that the wear-out stress causes the diffusant todiffuse from the reservoir into the diffusion region.

In some embodiments, the diffusion region comprises a semiconductormaterial.

In some embodiments, the indication of wear-out is associated with aconcentration of the diffusant in the diffusion region.

In some embodiments, the diffusant has a diffusion activation energybetween 0.75 eV and 2.5 eV in the diffusion region.

In some embodiments, the diffusant includes one or more elementsselected from the group consisting of aluminum (Al), cobalt (Co),platinum (Pt), sulfur (S), nickel (Ni), silver (Ag), zinc (Zn), gold(Au), chromium (Cr), copper (Cu), iron (Fe), sodium (Na), and potassium(K).

In some embodiments, the reservoir is formed at a surface of asubstrate, wherein the reservoir serves as a first electrode of thewear-out monitor device, and wherein the wear-out monitor device furthercomprises a second electrode formed at the surface and formed of amaterial different from the reservoir.

In some embodiments, the core circuit and the wear-out monitor deviceare formed in a common substrate formed of a semiconductor material andconfigured such that the diffusant remains in the wear-out monitordevice under a wear-out stress without diffusing into the core circuit.

In some embodiments, the integrated circuit device further comprises asensing circuit electrically connected to the wear-out monitor deviceand configured to detect an electrical property that changes in responseto the localized diffusion of the diffusant into the diffusion region.

In some embodiments, the integrated circuit device comprises the corecircuit that is physically separated from the wear-out monitor devicesuch that the diffusant does not diffuse into the core circuit from thewear-out monitor device.

In some embodiments, the wear-out monitor device is configured to beactivated by a stimulus prior to recording the indication of wear-out.

In some embodiments, the integrated circuit device further comprises acontrol circuit connected to the wear-out monitor device and configuredto supply the stimulus, wherein the stimulus comprises at least one of avoltage stimulus or a current stimulus.

In some embodiments, the stimulus comprises an optical stimulus.

In some embodiments, a physical barrier having an energy barrier fordiffusion of the diffusant is disposed between the reservoir and thediffusion region, wherein the physical barrier is configured such thatthe energy barrier is reduced in response to the stimulus to activatethe wear-out monitor device.

In some embodiments, the wear-out monitor device is configured such thatthe stimulus provides sufficient thermal energy to the barrier to reducethe energy barrier.

In some embodiments, the diffusion region and the reservoir havedifferent compositions such that the region has an energy barrier fordiffusion of the diffusant relative to the reservoir, wherein the energybarrier is such that the stimulus imparts sufficient energy to thediffusant to activate the wear-out monitor device.

In some embodiments, the energy barrier is greater than an averagethermal energy of the diffusant in the reservoir at room temperature.

In some embodiments, the wear-out monitor device comprises a pluralityof monitor structures each configured to record an indication ofwear-out of the core circuit.

In some embodiments, different ones of the monitor structures areconfigured to be activated by different stimuli prior to recordingindications of wear-out of the core circuit.

In some embodiments, the different ones of the monitor structures havedifferent physical barriers formed between the respective reservoirs andthe respective diffusion regions.

In some embodiments, different ones of the monitor structures havediffusion regions that are configured differently.

In some embodiments, the differently configured diffusion regions havedifferent compositions.

In some embodiments, different ones of the monitor structures havereservoirs that are configured differently.

In some embodiments, differently configured reservoirs have differentcompositions.

In some embodiments each of the monitor structures has a pluralityelectrodes formed thereon.

In some embodiments, electrodes of the plurality electrodes areregularly spaced apart from each other.

In some embodiments, the monitor structures are arranged laterally on acommon substrate.

In some embodiments, adjacent monitor structures are formed at regularintervals.

In some embodiments, the reservoir and the diffusion region are disposedlaterally relative to each other on a common substrate such that theindication of wear-out is based on the localized diffusion of diffusanthaving a net direction of diffusion in a lateral direction parallel to amajor surface of the substrate.

In some embodiments, the net direction of diffusion is a radially inwarddirection towards a centrally located diffusion region from a reservoirregion incorporating the diffusant that surrounds the diffusion region.

In some embodiments, the indication of wear-out is based on thediffusion of diffusant having a net direction of diffusion that is aradially outward direction from a centrally located reservoir regionincorporating the diffusant towards a diffusion region surrounding thereservoir region.

In some embodiments, the monitor structures are arranged vertically on acommon substrate.

In some embodiments, atoms of a substrate serves as the diffusant, suchthat the wear-out stress causes atoms of the substrate to diffuse fromthe substrate into the diffusion region.

In some embodiments, the wear-out stress causes formation of an oxidecomprising the atoms of the substrate a surface of the reservoir.

In some embodiments, the integrated circuit device further comprises asensing circuit electrically connected to the wear-out monitor deviceand configured to detect an electrical property that changes in responseto the localized diffusion of atoms of the substrate into the diffusionregion.

In some embodiments, the sensing circuit is configured to measure aresistivity of the diffusion region.

In some embodiments, the wear-out monitor device further includes areference electrode, wherein the sensing circuit is configured tomeasure a capacitance between the reference electrode and the diffusionregion.

In some embodiments, the wear-out monitor device is configured to applyan electric field to the diffusion region in a first direction, andwherein the diffusant has a charge state when diffused in the diffusionregion such that, when the electric field is applied to the diffusionregion having the diffusant diffused therein, the electric field causesthe diffusant to further diffuse in the diffusion region in the firstdirection.

In some embodiments, the diffusion region and the reservoir areadjacently disposed in a second direction different than the firstdirection and configured such that the wear-out stress causes thediffusant to diffuse in the second direction.

In some embodiments, the diffusion region is disposed in a semiconductorsubstrate and the reservoir is formed on a surface of the semiconductorsubstrate such that the wear-out stress causes the diffusant to diffusein a direction normal to the semiconductor substrate surface, and theelectric field causes the diffusant to diffuse in a direction parallelto the semiconductor substrate surface.

In some embodiments, a plurality of conductive structures are formed ona surface of the diffusion region along the first direction and provideelectrical access to the diffusion region at a plurality of locations.

In some embodiments, the wear-out monitor device is configured to applythe electric field by applying a voltage on one or more of theconductive structures.

In some embodiments, the diffusion region comprises a semiconductormaterial doped with a dopant having a concentration that is graded inthe first direction, such that the electric field varies in magnitudeacross the diffusion region in the first direction.

In some embodiments, the wear-out monitor has oppositely dopedsemiconductor regions in the diffusion region such that the electricfield is a built-in electric field in the diffusion region.

In some embodiments, the wear-out monitor device is configured such thatthe wear-out stress causes the diffusant to diffuse away from thereservoir and into the diffusion region, wherein the diffusant have acharge state when diffused into the diffusion region, and wherein thewear-out monitor device is further configured to apply an electric fieldto the diffusion region such that, when the electric field is applied tothe diffusion region having the diffusant diffused therein, the electricfield causes the diffusant to diffuse toward the reservoir.

In some embodiments, the wear-out monitor device is configured to applythe electric field having a magnitude such that, when the electric fieldis applied to the diffusion region having the diffusant diffusedtherein, the electric field causes the diffusant to diffuse in adirection of increasing concentration gradient.

In some embodiments, the wear-out monitor device is configured toactivate diffusion of the diffusant in response to a stimulus.

In some embodiments, the stimulus comprises at least one of a voltage, acurrent, light, or heat.

In some embodiments, the integrated circuit device further comprises acontrol circuit configured to apply the stimulus to the wear-out device.

In some embodiments, the integrated circuit device further comprises asensing circuit electrically connected to the wear-out monitor deviceand configured to provide an indication of a diffusion profile overtime.

In some embodiments, the integrated circuit device further comprises asensing circuit electrically connected to the wear-out monitor deviceand configured to provide an indication of wear-out in situ.

In some embodiments, the wear-out monitor device comprises asemiconductor substrate and the diffusant is configured to diffuse intothe semiconductor substrate.

In some embodiments, the integrated circuit device further comprises asensing circuit electrically connected to the wear-out monitor deviceand configured to detect an electrical property that changes in responseto the localized diffusion of diffusant into the semiconductorsubstrate.

In some embodiments, the integrated circuit device further comprises asensing circuit electrically connected to the wear-out monitor deviceand configured to detect an electrical property that changes in responseto localized diffusion of a semiconductor material of the wear-outmonitor device into a diffusion region.

In some embodiments, the wear-out monitor device is configured to enablea stimulus to be applied that causes a direction of the localizeddiffusion to change in response to the stimulus.

In another aspect, a method of monitoring wear-out of a core circuit ofan integrated circuit device uses a wear-out monitor device separatedfrom the core circuit. The method comprises recording an indication ofwear-out of the core circuit, wherein the indication is associated withlocalized diffusion of a diffusant within the wear-out monitor device inresponse to a wear-out stress that causes the wear-out of the corecircuit. The method additionally includes detecting an electricalproperty that changes in response to the localized diffusion of thediffusant. The method further includes reporting the electrical propertyof the wear-out monitor device.

In some embodiments, the method further comprises, prior to recording,subjecting the wear-out monitor device to the wear-out stress thatcauses the localized diffusion from a reservoir comprising the diffusantinto a diffusion region.

In some embodiments, the method further comprises, prior to subjectingthe wear-out monitor device to the wear-out stress, activating themonitor device by applying a stimulus to overcome an energy barrier.

In some embodiments, applying the stimulus alters a physical barrierhaving the energy barrier and reduces the energy barrier.

In some embodiments, the method further comprises, after subjecting thewear-out monitor device to the wear-out stress, applying an electricfield to the diffusion region having the diffusant diffused therein in afirst direction such that the electric field causes the diffusant tofurther diffuse in the first direction.

In some embodiments, the method further comprises, after subjecting thewear-out monitor device to the wear-out stress which causes thediffusant to diffuse away from the reservoir and into the diffusionregion, applying an electric field to the diffusion region having thediffusant diffused therein, such that the electric field causes thediffusant to diffuse toward the reservoir.

In another aspect, an integrated circuit device has wear-out monitoringcapability of a core circuit in the integrated circuit device. Theintegrated circuit device comprises means for recording an indication ofwear-out of a core circuit, wherein the indication is associated withlocalized diffusion of a diffusant within the means for recording inresponse to a wear-out stress that causes the wear-out of the corecircuit. The integrated circuit device additionally comprises means fordetecting the indication of wear-out of the core circuit, the means fordetecting the indication of wear-out being in communication with themeans for recording the indication of wear-out.

In some embodiments, the means for recording comprises a reservoircomprising the diffusant and a diffusion region in communication withthe reservoir such that the wear-out stress causes the diffusant todiffuse from the reservoir into the diffusion region.

In some embodiments, the means for recording is configured to activatein response to a stimulus prior to causing the diffusant to diffuse fromthe reservoir into the diffusion region.

In some embodiments, the integrated circuit device further comprisesmeans for applying an electric field to the diffusion region in a firstdirection, and wherein the diffusant has a charge state when diffused inthe diffusing region such that, when the electric field is applied tothe diffusing region having the diffusant diffused therein, the electricfield causes the diffusant to further diffuse in the diffusing region inthe first direction.

In some embodiments, the means for recording is configured such that thewear-out stress causes the diffusant to diffuse away from the reservoirand into the diffusion region, wherein the diffusant have a charge statewhen diffused into the diffusion region, and wherein the recording meansis further configured to apply an electric field to the diffusion regionsuch that, when the electric field is applied to the diffusion regionhaving the diffusant diffused therein, the electric field causes thediffusant to diffuse toward the reservoir.

In another aspect, a sensor includes an integrated data recordingstructure. The sensor includes a first region adapted to be exposed to amaterial which serves as a solute within a body of the sensor. Thesensor additionally includes a second region contacting the first regionand adapted to migrate the solute away from the first region such thatthe concentration of the solute as a function of time becomes encoded asa spatial distribution of the solute within the body of the sensor.

In some embodiments, the second region is configured to migrate thesolute in a first direction under an electric field (E-field).

In some embodiments, the E-field is an intrinsic E-field provided by aspatially graded doping profile within a material forming the secondregion.

In some embodiments, the E-field is provided by a voltage differenceapplied across the second region.

In some embodiments, the sensor further includes a read structureextending along the second region for reading electrical properties ofthe second region as a function of position along the second region.

In some embodiments, the read structure comprises a plurality ofelectrodes disposed along the second region.

In some embodiments, the read structure comprises a plurality oftransistors disposed along the second region, where the transistorscomprise bipolar junction transistors and the second region serves as abase region for respective ones of the bipolar transistors; and/or wherethe transistors comprise are field effect transistors and the secondregion acts as a gate or channel region for respective ones of the fieldeffect transistors.

In some embodiments, the read structure comprises a plurality of diodes.

In some embodiments, the sensor further includes a reference channel,where the reference channel comprises a third region corresponding tothe second region of the sensor, but not contacting the first region.

In some embodiments, a temperature comprises the sensor which includesthe integrated data recording structure described above. The firstregion of the sensor is in contact with or doped with the materialserving as the solute, where the material has an activation energy withrespect to a material of the body of the sensor of less than 3 electronvolts (eV).

In some embodiments, the material serving as the solute in thetemperature sensor is selected to have an activation energy less than 2eV and greater than 0.7 eV.

In some embodiments, the material in the temperature sensor is selectedfrom a group consisting of silver, gold and copper.

In some embodiments a concentration sensor comprises the temperaturesensor described above. In addition, the concentration sensor furthercomprises a third region exposed to a reagent which serves as a secondsolute; and a fourth region in contact with the third region and adaptedto migrate the second solute along the fourth region.

In some embodiments, the sensor further includes a structure forcontrolling contact between the material serving as the solute and thefirst region.

In some embodiments, the structure for controlling contact is responsiveto one or more of temperature, pressure and electrical control.

In some embodiments, the sensor further includes a read circuit.

In some embodiments, a die carries the sensor described above.

In some embodiments, a chip scale package comprises the die describedabove that is co-packaged with at least one other die.

In another aspect, a temperature sensor operable to record temperaturein an unpowered state comprises a solute material placed in contact witha memory region of a semiconductor. The memory region of thesemiconductor is doped such that an intrinsic electric field existstherein so as to migrate the solute along the memory region such thattemperature as a function of time becomes encoded as a spatialdistribution of solute within the memory region.

In another aspect, a method of manufacturing a temperature sensorcomprises adapting a region of a semiconductor such that an electricfield gradient exists across the region. The method additionallyincludes forming a plurality of read structures within the region of thesemiconductor configured such that electrical properties as a functionof position within the region can be determined. The method furtherincludes exposing a portion of the region of semiconductor to a sourceof impurities, whereby the impurities modify the electrical propertiesof the semiconductor.

For purposes of summarizing the disclosure, certain aspects, advantagesand novel features of the innovations have been described herein. It isto be understood that not necessarily all such advantages may beachieved in accordance with any particular embodiment. Thus, theinnovations may be embodied or carried out in a manner that achieves oroptimizes one advantage or group of advantages as taught herein withoutnecessarily achieving other advantages as may be taught or suggestedherein.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of this disclosure will now be described, by way ofnon-limiting example, with reference to the accompanying drawings.

FIG. 1 is a graph illustrating failure rate versus time for a populationof integrated circuit devices.

FIG. 2A illustrates an integrated circuit apparatus comprising anon-chip wear-out monitor device, according to embodiments.

FIG. 2B illustrates an integrated circuit apparatus comprising anon-chip wear-out monitor device and a reference device, according toembodiments.

FIGS. 3A and 3B illustrate a wear-out monitor device having monitoratoms whose rate of diffusion changes in response to a wear-out stress,according to embodiments.

FIG. 4A illustrates a wear-out monitor device having phosphorus asmonitor atoms, according to embodiments.

FIG. 4B is a graph illustrating calculated concentration profiles ofphosphorus in silicon substrate of the wear-out monitor device in FIG.4A, after diffusing at 125° C. for various times.

FIG. 5A illustrates a wear-out monitor device having gold as monitoratoms, according to embodiments.

FIGS. 5B-5D are graphs illustrating calculated concentration profiles ofgold in silicon substrate of the wear-out monitor device in FIG. 5A,after diffusing at 75° C., 100° C. and 125° C., respectively, forvarious times.

FIG. 6A is an illustration of a wear-out monitor device comprising asemiconductor material and monitor atoms configured to diffuse in thesemiconductor material, according to embodiments.

FIG. 6B illustrates a close up view of the boxed region of FIG. 6A.

FIG. 6C is a graph illustrating calculated concentration profiles ofgold in silicon device substrate of the wear-out monitor device in FIGS.6A/6B after diffusing at 125° C. for various times.

FIG. 7A is an illustration of a wear-out monitor device comprisingmonitor atoms configured to diffuse in a semiconductor material,according to embodiments.

FIG. 7B is an illustration of a reference device configured to providereference measurement for the monitor device of FIG. 7A, according toembodiments.

FIG. 8 is an illustration of a wear-out monitor device configured as acurrent-induced wear-out monitor device, according to embodiments.

FIG. 9 is an illustration of a wear-out monitor device configured as avoltage-induced wear-out monitor device, according to embodiments.

FIGS. 10A and 10B are illustrations of a wear-out monitor deviceconfigured as a PN junction wear-out monitor device, according toembodiments.

FIGS. 11A and 11B are illustrations of a wear-out monitor deviceconfigured as a vertical punch-through wear-out monitor device,according to embodiments.

FIG. 12 is an illustration of a wear-out monitor device configured as alateral punch-through wear-out monitor device, according to embodiments.

FIGS. 13A and 13B are illustrations of a wear-out monitor deviceconfigured as a metal-oxide-silicon (MOS) wear-out monitor device,according to embodiments.

FIGS. 14A and 14B illustrate a method of forming an electrodeincorporating monitor atoms for a wear-out monitor device, according toembodiments.

FIGS. 15A-15D illustrate various configurations of wear-out monitordevices comprising a PN junction and a layer of monitor atoms configuredto diffuse into the PN junction, according to embodiments.

FIGS. 16A-16G illustrate various configurations of wear-out monitordevices for controlling diffusion rate of monitor atoms into theunderlying substrate, according to embodiments.

FIGS. 17A and 17B illustrate wear-out monitor devices configured asbipolar junction transistors (BJTs), according to embodiments.

FIGS. 18A-18D illustrate wear-out monitor devices configured as metaloxide semiconductor (MOS) transistors, according embodiments.

FIGS. 19A and 19C-19D illustrate wear-out monitor devices configured asimpedance measurement devices, according to embodiments.

FIG. 19B schematically illustrate time evolution of concentrationprofile of wear-out monitor devices of FIGS. 19A and 19C-19D.

FIGS. 20A-20C illustrate conversion circuits configured to be used withwear-out monitor devices, according to some embodiments.

FIGS. 21A-21B illustrate conversion circuits configured to be used withwear-out monitor devices, according to some other embodiments.

FIGS. 22A-22C illustrate a capacitive programmable gain amplifier (PGA)circuits configured to compare output signals between a wear-out monitordevice and a reference device, according to embodiments.

FIGS. 23A-23C illustrate trans-impedance amplifiers (TIAs) configured toamplify and to convert current output of wear-out monitor devices to avoltage signal, according embodiments.

FIG. 24 illustrates a trans-impedance amplifier (TIA) with anode biasmultiplexed to amplify and to convert current outputs of a monitordevice and a reference device to a voltage signal, according to someembodiments.

FIG. 25 illustrates a lifetime indicator system having one or morewear-out monitor devices, according to embodiments

FIG. 26 illustrates a mission profile monitoring system comprising oneor more wear-out sensors, according to embodiments.

FIGS. 27-28 illustrate supply voltage guard-banding in IC devices forapplication of wear-out monitor devices, according to embodiments.

FIG. 29 illustrates an IC apparatus comprising a wear-out monitor deviceand configured to wirelessly transmit the monitored data while usingminimum or no energy, according to embodiments.

FIGS. 30A-30D illustrate various embodiments of wear-out monitor deviceshaving structures configured to oxidize or corrode for determiningcumulative wear-out stresses, according to embodiments.

FIG. 31 illustrates a plurality of wear-out monitor devices that arelaterally arranged as an array of wear-out monitor devices, according toembodiments.

FIGS. 32A and 32B illustrate a plurality monitor devices paired withreference devices and laterally arranged as an array, according toembodiments.

FIGS. 33A-33C illustrate a plurality of monitor devices that arelaterally arranged as an array, according to embodiments.

FIG. 34 is a diagram of a system in a package (SIP) or a system havingembedded components that includes one or more wear-out monitor devices,according to embodiments

FIGS. 35A and 35B illustrate schematic diagrams ESD event detectioncircuits configured as wear-out monitor devices, respectively, accordingto embodiments.

FIGS. 36A-36C illustrate example physical layouts of an ESD protectiondevices configured as wear-out monitor devices, according toembodiments.

FIG. 37A-37C schematically illustrate vertically integrated systems thatinclude one or more wear-out or corrosion monitor devices integratedwith ESD protection and/or energy harvesting circuitry on a single chip,according to embodiments.

FIGS. 38A-38E illustrate various embodiments of wear-out monitor devicesformed in or on a flexible substrate for monitoring wear-out stressesassociated with mechanical deformation, according to embodiments.

FIG. 39A illustrates a wear-out monitor device having one or moreserrated structures for monitoring wear-out stresses associated withelectric field enhancement, according to embodiments.

FIG. 39B illustrates a reference device for the wear-out monitor deviceof FIG. 39A, according to embodiments.

FIG. 40 is an illustration of a wear-out monitor device comprisingmonitor atoms configured to diffuse in a semiconductor material,according to embodiments.

FIG. 41A is a graph showing experimental current-voltage curves underreverse bias and breakdown under reverse bias of fabricated wear-outmonitor devices similar to the device schematically illustrated in FIG.40.

FIG. 41B is a graph showing experimental current-voltage curves underreverse bias of a fabricated wear-out monitor device similar to thedevice schematically illustrated in FIG. 40, after being subject todifferent durations of thermal stress at 200° C.

FIG. 41C is a graph showing experimental current-voltage curves underforward bias of a fabricated wear-out monitor device similar to thedevice schematically illustrated in FIG. 40.

FIG. 42A is a chart plotting experimental leakage currents under reversebias of a fabricated wear-out monitor device similar to the deviceschematically illustrated in FIG. 40, after being subject to differentdurations of thermal stress at 200° C.

FIG. 42B is a chart plotting calculated leakage currents under reversebias of a fabricated wear-out monitor device similar to the deviceschematically illustrated in FIG. 40, after being subject to differentdurations of thermal stress at different temperatures.

FIG. 42C is a contour chart plotting leakage currents under reverse biasof a fabricated wear-out monitor device similar to the deviceschematically illustrated in FIG. 40, as a function of differentdurations and temperatures of thermal stress.

FIG. 43A illustrates a wear-out monitor device configured to record anindication of wear out of a core circuit based on localized atomicdiffusion of monitor atoms, where the device has a reservoir of monitoratoms that is separated from the substrate by a barrier, according toembodiments.

FIG. 43B illustrates a simulation of Joule-heating caused by anelectrical stimulus applied to the wear-out monitor device illustratedin FIG. 43A, according to embodiments.

FIG. 44A illustrates a schematic three-dimensional energy-space diagramillustrating activation energy levels for a monitor atom, according toembodiments.

FIG. 44B illustrates a schematic two-dimensional energy-space diagramillustrating activation energy levels for a monitor atom in a wear-outmonitor device having a reservoir of monitor atoms that is separatedfrom the substrate by a physical barrier, according to embodiments.

FIG. 45 illustrates a schematic two-dimensional energy-space diagramillustrating activation energy levels for a monitor atom in a wear-outmonitor device having an energy barrier between a reservoir of monitoratoms and a monitor region, according to embodiments.

FIG. 46 illustrates a wear-out monitor device configured to record anindication of wear out of a core circuit based on localized atomicdiffusion of monitor atoms, where the device has a reservoir of monitoratoms that is separated from the substrate by a physical barrier, andhaving an energy barrier between a reservoir of monitor atoms and amonitor region, according to embodiments.

FIG. 47 illustrates a wear-out monitor device configured to record anindication of wear out of a core circuit based on localized atomicdiffusion of monitor atoms, where the device has an energy barrierbetween a reservoir of monitor atoms and a monitor region, according toembodiments.

FIG. 48 illustrates a wear-out monitor device configured to record anindication of wear out of a core circuit based on localized atomicdiffusion of monitor atoms, where a reservoir of monitor atoms isseparated from the substrate by a physical barrier, according toembodiments.

FIG. 49A illustrates a wear-out monitor device configured to record anindication of wear out of a core circuit based on localized atomicdiffusion of monitor atoms, where the device has an energy barrierbetween a reservoir of monitor atoms and a monitor region, according toembodiments.

FIG. 49B illustrates a cross-sectional view of an example electricalstimulus applied to the reservoir of the wear-out monitor deviceillustrated in FIG. 49A, according to embodiments.

FIG. 49C illustrates a cross-sectional view of the simulated currentdensity distribution resulting from the electrical pulse illustrated inFIG. 49B.

FIG. 49D illustrates a cross-sectional view of the simulated heatdistribution resulting from the Joule heating.

FIG. 49E illustrates a cross-sectional view of the simulated impactionization resulting from the electrical pulse illustrated in FIG. 49B.FIG. 49F illustrates a cross-sectional view of the simulated potentialgradient resulting from the electrical pulse illustrated in FIG. 49B.

FIG. 50A illustrates a cross-sectional view of a wear-out monitor deviceconfigured to record an indication of wear out of a core circuit basedon localized atomic diffusion of monitor atoms, where the wear-outmonitor device includes a plurality of monitor structures, according toembodiments.

FIG. 50B illustrates an example control circuit having a current supplytransistor electrically connected to and configured to supply theelectrical stimulus to the wear-out monitor device illustrated in FIG.50A, according to embodiments.

FIG. 51A illustrates a cross-sectional view (upper drawing) and atop-down plan-view (lower drawing) of a wear-out monitor deviceconfigured to record an indication of wear out of a core circuit basedon localized atomic diffusion of monitor atoms, according toembodiments.

FIG. 51B illustrates a cross-sectional view of a wear-out monitor deviceconfigured to record an indication of wear out of a core circuit,according to some other embodiments.

FIG. 52 illustrates a top-down plan-view of a wear-out monitor deviceconfigured to record an indication of wear out of a core circuit basedon localized atomic diffusion of monitor atoms, where the wear-outmonitor device includes an array having a plurality of rows, accordingto embodiments.

FIG. 53 illustrates a top-down plan-view of a wear-out monitor deviceconfigured to record an indication of wear out of a core circuit basedon localized atomic diffusion of monitor atoms that is localized withinthe wear-out monitor device, where the wear-out monitor device includesan array having a plurality of monitor structures arranged at differentradial distances from a reference point or a central position, accordingto embodiments.

FIGS. 54A and 54B illustrate a cross-sectional view and a top downplan-view of a wear-out monitor device configured to record anindication of wear out of a core circuit based on localized atomicdiffusion of monitor atoms in a radially outward direction, according toembodiments.

FIG. 55A illustrates a plan-view of a wear-out monitor device that isconfigured to record an indication of wear out of a core circuit basedon localized atomic diffusion in a radially inward direction, where thewear-out monitor device includes a plurality of monitor structuresincluding a barrier, according to embodiments.

FIG. 55B illustrates a plan-view of a wear-out monitor device that isconfigured to record an indication of wear out of a core circuit basedon localized atomic diffusion in a radially inward direction, where thewear-out monitor device includes a plurality of monitor structures eachincluding a different barrier, according to embodiments.

FIG. 55C illustrates a plan-view of a wear-out monitor device that isconfigured to record an indication of wear out of a core circuit basedon localized atomic diffusion in a radially inward direction, where thewear-out monitor device includes a plurality of monitor structures eachincluding a different barrier and a different reservoir, according toembodiments.

FIG. 56A illustrates a cross-sectional view of a wear-out monitor devicethat is configured to record an indication of wear out of a core circuitbased on localized atomic diffusion in a lateral direction, where thewear-out monitor device includes a plurality of monitor structuresincluding a barrier and differently configured monitor regions,according to embodiments.

FIG. 56B illustrates the wear-out monitor device illustrated in FIG.56A, further illustrating electrical connections to different regions ofthe wear-out monitor device, according to embodiments.

FIG. 56C illustrates an equivalent circuit diagram of the wear-outmonitor device illustrated in FIG. 56A that is configured to beinitialized by individually applying an electrical stimulus to arespective region of the barrier between the reservoir and the each ofthe monitor regions, according to embodiments.

FIG. 56D illustrates one example embodiment of a sensing circuitelectrically connected to the wear-out monitor device illustrated inFIG. 56A that is configured to measure changes in electrical propertiesof the monitor regions, according to embodiments.

FIG. 56E illustrates a cross-sectional view of a wear-out monitor devicethat is configured to record an indication of wear out of a core circuitbased on localized atomic diffusion in a lateral direction, where thewear-out monitor device includes two sets of monitor regions commonlyconnected to a reservoir, according to embodiments.

FIG. 57 illustrates a cross-sectional view of a wear-out monitor devicethat is configured to record an indication of wear out of a core circuitbased on localized atomic diffusion, where a plurality of reservoirs ofmonitor atoms are configured as wire bonds, according to embodiments.

FIG. 58 illustrates a cross-sectional view of a wear-out monitor devicethat is configured to record an indication of wear out of a core circuitbased on localized atomic diffusion, where a plurality of reservoirs ofmonitor atoms are configured as different wire bonds, according toembodiments.

FIG. 59 illustrates a plan-view of a plurality of wear-out monitordevices that are embedded or incorporated as part of a package-levelintegrated system along with other passive/discrete components and/ormicroprocessors that include core circuits to be protected, according toembodiments.

FIG. 60A illustrates a cross-sectional view of a package-levelintegrated system including a plurality of wear-out monitor devices thatare embedded or incorporated with other passive/discrete componentsand/or microprocessors that include core circuits to be protected, wherethe barrier is formed of a material that is configured to be altered byphotons of light, according to embodiments.

FIG. 60B illustrates the system illustrated in FIG. 60A mounted onanother system that includes control and/or sensing circuitry, accordingto embodiments.

FIG. 61 illustrates a wear-out monitor device configured to record anindication of wear out of a core circuit based on localized atomicdiffusion of monitor atoms, where the indication is based oninterdiffusion between the monitor region and the reservoir of monitoratoms, according to embodiments.

FIG. 62A illustrates a wear-out monitor device configured to record anindication of wear out of a core circuit based on localized atomicdiffusion of monitor atoms, where the indication is based oninterdiffusion between the monitor region and the reservoir of monitoratoms, according to embodiments.

FIG. 62B illustrates a close-up view of the wear-out monitor deviceillustrated in FIG. 62A electrically connected to a sensing circuitconfigured to detect electrical signatures associated with thestructural modifications to the reservoir resulting from interdiffusionof atoms, according to embodiments.

FIGS. 63A-63D illustrate cross-sectional views of a wear-out monitordevice configured such that electrical signatures based oninterdiffusion of atoms can be utilized to measure wear-out of a corecircuit, according to embodiments.

FIG. 64A illustrates concentration profiles of monitor atoms resultingfrom a cumulative equivalent constant thermal wear-out stress.

FIG. 64B illustrates concentration profiles of monitor atoms resultingfrom a cumulative time-varying thermal wear-out stress.

FIG. 65 is a graph comparing temperature fluctuations against an averagetemperature and against a moving average temperature

FIGS. 66A-66C is a schematic diagram of a temperature sensor accordingto some embodiments.

FIG. 67 a schematic diagram of a temperature sensor, according to someother embodiments.

FIG. 68 is a schematic diagram of a temperature sensor including anexternal voltage source for migrating diffused material along the bodyof the sensor, according to embodiments.

FIG. 69 is a diagram schematically illustrating dopant density within asensor according to embodiments.

FIG. 70A schematically illustrates a graded (stepped) dopingconcentration profile as a function of distance within a sensoraccording to an embodiment.

FIG. 70B schematically illustrates an electric field as a function ofdistance corresponding to the doping concentration profile of FIG. 14 a;

FIG. 70C schematically illustrates an electric potential correspondingto the doping concentration profile of FIG. 14 a;

FIG. 71 schematically illustrates the migration of a diffused region ofmaterial as a function of time under the influence of the electricfield.

FIG. 72 is a graph showing the combined effects of diffusion and drifts.

FIG. 73 is a cross section view of a read structure, according toembodiments.

FIG. 74 is a plan view of the read structure of FIG. 17.

FIG. 75 is a cross section through the read structure of FIG. 17 alongline A-A′.

FIG. 76 is a plan view of an alternative read structure, according toembodiments.

FIG. 77 shows a first arrangement for isolating the material thatprovides the solute from the first region, according to embodiments.

FIG. 78 shows a second arrangement for isolating the solute from thefirst region, according to embodiments.

FIG. 79 is a schematic diagram of a data acquisition circuit for usewith a sensor of the present disclosure, according to embodiments.

FIG. 80 shows a die carrying an embodiment of the present disclosureco-packaged with a functional circuit in a chip scale package, accordingto embodiments.

FIG. 81 is a plan view of a concentration sensor constituting anembodiment of this disclosure, according to embodiments.

FIG. 82 shows an embodiment having a clear/reset function, according toembodiments.

FIG. 83 illustrates a wear-out monitor device configured fortime-resolved monitoring of wear-out of a core circuit, according toembodiments.

FIG. 84 illustrates a wear-out monitor device configured fortime-resolved monitoring of wear-out of a core circuit, according toembodiments.

FIG. 85 illustrates a plurality of wear-out monitors, in which differentones of the wear-out monitor devices can be enabled and co-ordinatedusing a combination of different features described above, depending onthe application, according to embodiments.

FIG. 86 illustrates a plurality of wear-out monitors arranges in anarray, where accessing individual diffusion monitor devices can beco-ordinated by fuses, according to embodiments.

FIG. 87 illustrates an arrangement of wear-out monitors comprising aplurality of wear-out monitors or regions each connected to a transistorand a sensing circuitry for time-resolved monitoring, according toembodiments.

FIG. 88 illustrates a wear-out monitor comprising a plurality ofreservoirs each comprising monitor atoms that are separated from asubstrate by a barrier, according to embodiments.

FIG. 89 illustrates wear-out monitor comprising a substrate havingformed thereon a reservoir of monitor atoms and a plurality ofelectrodes for time-resolved monitoring, where the substrate isconnected to a “fast forward” and/or a “rewind” circuitry for laterallydiffusing the monitor atoms, according to embodiments.

FIG. 90 illustrates wear-out monitor comprising a substrate havingformed thereon a reservoir of monitor atoms and a plurality ofelectrodes for time-resolved monitoring, where the electrodes areconnected to a reverse bias leakage multiplexed measurement circuitry,according to embodiments.

FIG. 91 illustrates the electrodes being connected to a reverse biasleakage multiplexed measurement circuitry comprising a referencestructure for differential measurements, according to embodiments.

FIG. 92 illustrates wear-out monitor comprising a substrate havingformed thereon a reservoir of monitor atoms and a plurality ofelectrodes for time-resolved monitoring, where a plurality of monitorMOS transistors whose gates serve as the electrodes, according toembodiments.

FIG. 93 illustrates wear-out monitor comprising a substrate havingformed thereon a reservoir of monitor atoms and a plurality ofelectrodes for time-resolved monitoring, where a plurality of monitorMOS transistors whose gates serve as the electrodes, according toembodiments.

FIG. 94 illustrates the electrodes being connected to a reverse biasleakage multiplexed measurement circuitry comprising a referencestructure for differential measurements, where the measurement circuitryis configured to measure reverse bias recovery current, according toembodiments.

FIG. 95A illustrates a sensing circuit configured to measure reversebias recovery current and comprising a monitor diode for monitoringwear-out of a core circuit, according to embodiments.

FIG. 95B illustrates the measured current as the monitor diode isswitched from a forward biased configuration to a reverse biasedconfiguration, using the sensing circuit illustrated in FIG. 96A.

FIG. 96A illustrates a sensing circuit comprising a reference diode,which does not have impurities diffused therein.

FIG. 96B illustrates the measured current as the reference diode of FIG.96A is switched from a forward biased configuration to a reverse biasedconfiguration, using the sensing circuit illustrated in FIG. 96A.

FIG. 97 illustrates a wear-out monitor device having monitor atoms thatare adapted to have a charge state when diffused in the monitor region,and configured to apply an electric field to the monitor region suchthat, when the electric field is applied to the monitor region havingthe monitor atoms diffused therein, the electric field causes themonitor atoms to diffuse away from the monitor region and back into thereservoir.

FIG. 98 illustrates a system including sensing and/or control circuitryelectrically connected to various regions of the wear-out monitor deviceillustrated in FIG. 97, according to embodiments.

FIG. 99 illustrates a sensor network system configured for monitoringwear-out of a core circuit, according to embodiments.

FIG. 100 illustrates a sensor network communicatively coupled to a anupstream system, according to embodiments.

FIG. 101 illustrates a sensor network communicatively coupled to cloudhosted services, according to embodiments.

FIG. 102 illustrates a sensor network in which the sensors areconfigured to collect data by communicating directly with a privateserver or hosted services, according to embodiments.

FIG. 103 illustrates various physical and electrical connections thatcan be made to various wear-out monitor devices, for integration into asensor network system, according to embodiments.

FIG. 104 illustrates an example sensor network system based on wear-outmonitor devices according to embodiments.

FIG. 105 illustrates a sensor network communicatively coupled with ahosted service, according to embodiments.

FIG. 106 illustrates a sensor network communicatively coupled with ahosted service, according to embodiments.

DETAILED DESCRIPTION

The following detailed description of certain embodiments presentsvarious descriptions of specific embodiments. However, the innovationsdescribed herein can be embodied in a multitude of different ways, forexample, as defined and covered by the claims. In this description,reference is made to the drawings where like reference numerals canindicate substantially identical or functionally similar elements. Itwill be understood that elements illustrated in the figures are notnecessarily drawn to scale. Moreover, it will be understood that certainembodiments can include more elements than illustrated in a drawingand/or a subset of the elements illustrated in a drawing. Further, someembodiments can incorporate any suitable combination of features fromtwo or more drawings. The headings provided herein are for convenienceonly and do not necessarily affect the scope or meaning of the claims.

As described herein, wear-out of an IC device refers to a degradationphenomenon of any component or subcomponent of the IC device caused byusage or environmental factors. As disclosed herein, wear-out monitordevices according to embodiments can monitor wear-out of core circuitry,with or without a power supply, and are capable of monitoring arelatively large range of physical conditions. In addition, wear-outmonitors according to embodiments disclosed herein can be integrated,e.g., monolithically integrated, in the same substrate as a core circuitof an IC. The wear-out monitor devices according to embodiments utilizediffusion of a diffusant within or in a diffusion region to record anindication of wear-out of a core device. That is, embodiments utilizeatomic diffusion of certain diffusing atoms, also referred to herein asmonitor atoms, in a diffusion region, also referred to herein as monitorregion, which can be, e.g. a region in a semiconductor substrate, e.g.,a silicon substrate, to monitor, record, and store electrical signaturesassociated with wear-out mechanisms (e.g., temperature, voltage,current, or any combination thereof) over a lifetime of the product. Themonitor atoms can be integrated as part of a wear-out monitor device,where the net movement of monitor atoms caused by wear-out stresses,e.g., from a reservoir to a diffusion region in communication with thereservoir, alters the an electrical signature of the wear-out monitordevice. The electrical signature can be monitored at any point duringthe lifetime of the product to quantify the degree of wear-out of coredevices in the IC. Since the movement of the monitor atoms can occurwithout a separate power supply, the wear-out monitor device can beconsidered to be “passive.”

Embodiments of this disclosure can provide many advantages. For example,electrical signatures associated with the wear-out state of an IC deviceover its lifetime can be recorded without a power supply because theeffective “power supply” for the monitor device is provided by theconcentration gradient of the dopant concentration, which provides thedriving force for the diffusion of monitor atoms. Alternatively oradditionally, the movement of the monitor atoms, which can beirreversible, provides a method to “record” cumulative stress(es) theproduct has been exposed to over a period of time. Alternatively oradditionally, because a diffusion mechanism can work over a wide rangeof conditions beyond the service temperatures of ordinary sensors andtheir supporting circuitry, the disclosed wear-out monitor devices canprovide signatures of cumulative stresses at relatively extremeconditions. Alternatively or additionally, the choice of suitablemonitor atoms as the diffusing species can advantageously be made inconjunction with the choice of a suitable device geometry to monitordifferent wear-out effects at different conditions, e.g., underdifferent temperature and electric field ranges for different periods oftime. In certain embodiments, a reference device can be used to providea reference “initial condition” against which a quantitative monitoringof the time evolution of the monitor atoms can be made, as well as todifferentiate drift and noise to enhance the accuracy of the wear-outmonitor devices. For example, the wear-out monitor device can havemonitor atoms (disclosed infra) that diffuse substantially in thesubstrate in addition to a “traditional” dopant (e.g., p-type dopants Band n-type dopants P and As in silicon) that does not diffusesubstantially in the semiconductor substrate, while the reference devicecan omit the monitor atoms, such that the reference device provides asemi-permanent “initial condition” that can be provided as theconcentration profile of the monitor atoms evolves under wear-outconditions.

FIG. 1 is a graph 10 schematically illustrating rates (y-axis) offailure of different failure mechanisms versus time (x-axis) for a givenpopulation of similarly manufactured IC devices. Wear-out failuremechanisms can generally be categorized into three categories: early“infant mortality” failure, whose failure rate dominates at early stagesand decreases over a device service time, represented by the failurerate curve 16; random failure, whose failure rate is relativelyindependent of the device service time, represented by the failure ratecurve 14; and wear-out failure, whose failure rate increases over thedevice service time, represented by the failure rate curve 12. Theobserved overall failure rate curve 18, sometimes referred to as a“bathtub curve,” can be represented by the sum of the three failure ratecurves 12, 14 and 16, and can be described as having three regions: adecreasing failure rate region, followed by a relative constant failurerate region, followed by an increasing failure rate region.

As wafer fab geometries/structures continue to shrink in feature size(e.g., critical lithography dimensions), it has been observed that therelative duration of the constant failure region decreases, and that theincreasing failure region dominated by wear out failures is reached atan increasingly service time. Based on this observation, with decreasingfeature size, there is an increasing need to be able to identifycomponents, subcomponents or structures within a semiconductor die thatare may be in the wear-out failure phase and to flag them sufficientlyearly such that appropriate action can be taken before catastrophicfailure occurs. There is also an increasing need to be able to real-timemonitor the actual mission profile/operating conditions of IC devices inthe field (as opposed to supposed/theoretical), and where deviationsoccur, to be able to flag such that appropriate actions can be taken.

IC Apparatuses Comprising Wear-Out Monitor Devices

FIGS. 2A and 2B illustrate integrated circuit (IC) apparatuses 20 a and20 b each comprising a wear-out monitor device 24 a/24 b, e.g., anon-chip wear-out monitor device, according to various embodiments. Eachof the IC apparatuses 20 a and 20 b has a core circuit 22 a/22 b and awear-out monitor device 24 a/24 b for monitoring various types ofcumulative stresses (e.g., temperature, voltage, current, etc. or anycombination thereof). In various embodiments, the wear-out monitordevice 24 a/24 b is configured to adjust an indication of wear out ofthe core circuit 22 a/22 b regardless of whether the core circuit isactivated. In some embodiments, the core circuit 22 a/22 b and thewear-out monitor device 24 a/24 b are formed in a common semiconductorsubstrate of the IC apparatuses 20 a and 20 b, such that they can besubject to common wear-out stresses. In some embodiments, the corecircuit 22 a/22 b and the wear-out monitor device 24 a/24 b areelectrically separated from each other while being formed in a commonsemiconductor substrate of the IC apparatuses 20 a and 20 b, such thatthey can be subject to common wear-out stresses. For example, formonitoring thermal wear-out, the core-circuit 22 a/22 b and the monitordevice 24 a/24 b formed in a common substrate can be in thermalcommunication with each other. For monitoring electrical wear-out, thecore-circuit 22 a/22 b and the monitor device 24 a/24 b formed in acommon substrate can be electrically connected with each other in closeproximity and fabricated using similar processes. For monitoringmechanical wear-out, the core-circuit 22 a/22 b and the monitor device24 a/24 b formed in a common substrate can be subjected to similarmechanical stress, e.g., elongation, bending, thermal expansion, etc. Asa result, cumulative physical stresses experienced by the monitor device24 a/24 b are representative of the cumulative physical stressesexperienced by the core circuit 22 a/22 b. Each of the IC apparatuses 20a and 20 b includes a sensing circuit 26 a/26 b coupled to the wear-outmonitor device 24 a/24 b. Unlike the IC apparatus 20 a of FIG. 2A, theIC apparatus 20 b of FIG. 2B additionally has a reference device 28 belectrically connected to the sensing circuit 26 b for quantitativedetermination of the wear-out state of devices in the core circuit 22 b.

As described herein and throughout the specification, it will beappreciated that the semiconductor substrates in which IC apparatusesare fabricated can be implemented in a variety of ways, including, butnot limited to, a doped semiconductor substrate, which can be formed ofan elemental Group IV material (e.g., Si, Ge, C or Sn) or an alloyformed of Group IV materials (e.g., SiGe, SiGeC, SiC, SiSn, SiSnC, GeSn,etc.); Group III-V compound semiconductor materials (e.g., GaAs, GaN,InAs, etc.) or an alloy formed of Group III-V materials; Group II-VIsemiconductor materials (CdSe, CdS, ZnSe, etc.) or an alloy formed ofGroup II-VI materials. The semiconductor substrate can be formed of hightemperature materials such as SiC for applications where monitoringtemperature is expected to exceed about 500° C.

According to certain embodiments, the substrate can be implemented as asemiconductor on insulator, such as silicon on insulator (SOI)substrate. An SOI substrate typically includes asilicon-insulator-silicon structure in which the various structuresdescribed above are isolated from a support substrate using an insulatorlayer such as a buried SiO₂ layer. In addition, it will be appreciatedthat the various structures described herein can be at least partiallyformed in an epitaxial layer formed at or near a surface region.

Wear-Out Monitor Device Structures

FIGS. 3A and 3B illustrate a wear-out monitor device 30 a/30 b havingmonitor atoms whose rate of diffusion changes in response to a stresscondition, according to embodiments. The wear-out monitor device 30 arepresents an initial monitor device prior to being subjected to awear-out stress, e.g., a thermal stress, and the wear-out monitor device30 b represents the monitor device after being subjected to the wear-outstress. The wear-out monitor device 30 a/30 b comprises a semiconductormaterial 32 a/32 b, e.g., a semiconductor substrate that is doped withdopant of first type, e.g., a donor-type dopant to a concentrationN_(d), and monitor atoms 34 a, e.g., an acceptor-type dopant to aconcentration N_(a). The monitor atoms 34 a are configured to diffuse inor into the semiconductor material 32 a under a wear-out stress, and therate at which the monitor atoms 34 a diffuse change according to thelevel of the wear-out stress.

Referring to FIG. 3A, an initial schematic concentration profile 36 athrough a section AA′ of the initial wear-out monitor device structure30 a shows a relatively abrupt concentration profile of the monitoratoms N_(a) in the vertical direction (x). Referring to FIG. 3B, afterthe initial wear-out device structure 30 a (FIG. 3A) is subjected to awear-out stress, e.g., a thermal wear-out stress, the monitor atoms 34 adiffuse into the semiconductor material 32 a, resulting in post-stresswear-out monitor device structure 30 b (FIG. 3B), in which the monitoratoms 34 b has diffused into the semiconductor material 32 b. Theresulting schematic concentration profile 36 b through a section BB′ ofthe post-stress wear-out monitor device structure 30 b shows arelatively diffused concentration profile of N_(a) in the verticaldirection (x). As described infra, the change in concentration profileof monitor atoms N_(a) can be electrically detected using variousmethods. Such change, which results from the cumulative wear-out stresson the wear-out monitor device 30 a, can induce a corresponding changein electrical properties of the monitor device structure 30 a/30 b, fromwhich the wear-out level of the core circuit 22 a/22 b (FIGS. 2A/2B) canbe determined.

Of course, in FIGS. 3A and 3B and throughout the specification, it willbe appreciated that while monitor atoms 34 a may be represented asacceptor-type dopants, the embodiments are not so limited. The monitoratoms can be donor-type dopants, or not be dopants at all, but ratherimpurities. Furthermore, monitor atoms 34 a may be present in additionto dopants, which may be acceptor-type or donor-type dopants.

It will further be appreciated in FIGS. 3A/3B and throughout thespecification that monitor atoms 34 a may include one or more chemicalelements.

FIG. 4A illustrates a wear-out monitor device 40 according toembodiments. The wear-out monitor device 40 comprises a semiconductorsubstrate 42 doped with a dopant of a first type, e.g., a donor, to aconcentration of N_(d), and monitor atoms 44 having a concentrationN_(a). A schematic initial concentration profile 46 a through a sectionCC′ shows a relatively abrupt concentration profile of N_(a) in avertical direction (x), while a schematic post-stress concentrationprofile 46 b through the section CC′ shows a relatively diffusedconcentration profile of N_(a) in the vertical direction (x). In theparticular illustrated embodiment, the simulated monitor atoms 44 arephosphorus atoms diffusing in silicon at 125° C.

FIG. 4B is a graph 48 of calculated concentration profiles of monitoratoms 44 of the monitor device 40 of FIG. 4A, according to embodiments.In the illustrated embodiment, the calculated concentrations are thoseof phosphorus (P) atoms in silicon after diffusing for various timesranging from 10⁴ years to 10⁷ years, in which the x-axis represents thex-axes of schematic concentration profiles 46 a and 46 b of FIG. 4A, andin which the origin corresponds to the initial interface between theN_(d) profile and the N_(a) profile of the concentration profile 46 a.As the graph 48 illustrates, because of relatively low diffusion rate ofP in Si at 125° C., appreciable diffusion as measured by, e.g., adiffusion length at which the concentration has fallen to about 1% of aninitial concentration, is less than 0.1 nm after 10,000 years. That is,based on the calculation, under some circumstances, e.g., idealconditions, phosphorus may not be monitor atoms for monitoring changesin the rate of diffusion under thermal wear-out stress.

As illustrated by FIGS. 4A/4B, it will be appreciated that selectingappropriate monitor atoms for a given diffusing medium, e.g.,semiconductor substrate, can be important for effective wear-out monitordevices. Diffusivity can be expressed as:

$\begin{matrix}{{D(T)} = {D_{0}\mspace{11mu}{{\exp\left\lbrack \frac{E_{a}}{kT} \right\rbrack}.}}} & {{Eq}.\;\lbrack 1\rbrack}\end{matrix}$

Inventors have found that selecting a monitor atom/diffusing mediumcombination to have the diffusion activation energy (Ea) in a certainrange, is desirable. For example, the diffusivity of phosphorus insilicon is activated by an activation energy of 3.66 eV, which resultsin a wear-out monitor device that may impractical for use as a thermalstress monitor under ideal circumstances, as described above. Forillustrative purposes and without being bound to any theory or accuracyof the parameters, diffusivities of selected atoms in silicon are aslisted in TABLE 1:

TABLE 1 Diffusivity of Selected Atoms and Molecules in Crystalline SiDiffusion Activation Element Diffusivity, D(T) (cm²/sec) Energy (eV) B0.76 × 10⁻⁴ exp(−3.46/kT) 3.46 P 3.85 × 10⁻⁴exp(−3.66/kT) 3.66 Sb 0.214× 10⁻⁴exp(−3.65/kT) 3.65 Al 0.5 × 10⁻⁴exp(−3.0/kT) 3.0 Co (9.2 ×10⁻⁴)exp(−2.8/kT) 2.8 Pt (1.5 × 10²)exp(−2.22/kT) 2.22 S(0.92)exp(−2.2/kT) 2.2 Ni (0.1)exp(−1.9/kT) 1.9 Ag (2.0 ×10⁻³)exp(−1.6/kT) 1.6 Zn (0.1)exp(−1.4/kT) 1.4 Au (1.1 ×10⁻³)exp(−1.12/kT) 1.12 Cr (0.01)exp(−1.0/kT) 1.0 Cu (4.0 ×10⁻³)exp(−1.0/kT) 1.0 Fe (6.2 × 10⁻³)exp(−0.87/kT) 0.87 Na (1.6 ×10⁻³)exp(−0.76/kT) 0.76 K (1.1 × 10⁻³)exp(−0.76/kT) 0.76 H₂ (9.4 ×10⁻³)exp(−0.48/kT) 0.48

The inventors have found that the activation energy Ea of diffusivitycan be one criteria for choosing the monitor atoms to be used in thewear-out monitor devices according to embodiments. In some embodiments,the monitor atoms have a diffusion activation energy in thesemiconductor substrate that is between about 0.5 eV and about 3.5 eV,between about 0.75 eV and about 2.5 eV, or between about 1.0 eV andabout 1.6 eV, depending on the anticipated thermal and/or electricalwear-out stresses. Based on TABLE 1 above, suitable atoms can includeAl, Co, Pt, S, Ni, Ag, Zn, Au, Cr, Cu, Fe, Na and K, to name a few.Moreover, suitable monitor atoms can include two or more elements incertain embodiments. For instance, monitor atoms can include two or moreof the following elements: Al, Co, Pt, S, Ni, Ag, Zn, Au, Cr, Cu, Fe, Naor K.

By way of example, FIGS. 5A-5D illustrate time evolution ofconcentration profiles of gold (Au) in silicon at temperatures of 75°C., 100° C. and 125° C. for durations ranging from 1 year to 10 years.Referring to FIG. 5A, a schematic initial concentration profile 50 a anda schematic post-stress concentration profile 50 b of a wear-out monitordevice structure (not shown) similar to the wear-out monitor devicestructure 40 of FIG. 4A are illustrated. Unlike the schematicconcentration profiles 46 a and 46 b of FIG. 4A in which the monitoratoms are phosphorus (P) atoms with an activation energy of 3.66 eV, theschematic concentration profiles 50 a and 50 b represent those in whichthe monitor atoms are gold (Au) atoms. Referring to FIGS. 5B-5D, graphs52, 54 and 56 illustrate calculated concentration profiles of gold insilicon at 75° C., 100° C. and 125° C., respectively, after diffusingfor various times ranging from 1 year to 10 years, in which the x-axesrepresents the vertical diffusing direction similar to the x-directionthrough the section CC′ of FIG. 4A, and in which the origin correspondsto the initial interface between the N_(d) profile and the N_(a)profile. As the graphs 52, 54 and 56 illustrate, Au has diffusion ratein Si at temperatures of 75° C., 100° C. and 125° C. that are morepractical for monitoring changes in rate of diffusion under thermalstress. For example, for Au, a diffusion length at which theconcentration has fallen to about 1% of an initial concentration isbetween about 160 nm and about 1600 nm after about 10 years at 75° C.and 125° C., respectively. That is, based on FIGS. 5B-5D, Au in Si canbe a more practical diffusion system for monitoring changes in rate ofdiffusion under thermal wear-out stress.

FIG. 6A illustrates a wear-out monitor device 60 having monitor atomshaving a diffusion activation energy in the substrate that is betweenabout 0.5 eV and about 3.5 eV, according to embodiments. FIG. 6B is aclose up view of the region in the dotted box of FIG. 6A. Similar to ICdevices 20A and 20B of FIGS. 2A and 2B, the wear-out monitor device 60comprises a semiconductor substrate 62 and monitor atoms configured todiffuse therein, wherein the monitor atoms are configured such that astress condition causes a change in the rate at which the monitor atomsdiffuse in the semiconductor substrate 62.

The wear-out monitor device 60 includes a first doped region 64 dopedwith a first dopant type, which can be n-type or p-type. In theillustrated embodiment of FIGS. 6A/6B, the first doped region 64 is aheavily doped p-doped region, e.g., a heavily doped (p⁺) region.

The wear-out monitor device 60 additionally includes a second dopedregion 66 that is doped with a second dopant type opposite to the firstdopant type, i.e., p-doped when the first doped region 64 is n-doped,and vice versa. In the illustrated embodiment, the second doped region66 is an n-doped region, e.g. a heavily doped (n+) region.

In some embodiments, the wear-out monitor device 60 additionally mayinclude an intervening region 65 interposed between the first and seconddoped regions 64, 66 that is doped either with the first or seconddopant types, at a concentration substantially lower than the first orsecond doped regions 64 or 66. In the illustrated embodiment, theintervening region 65 is a p-doped region. Thus, the wear-out monitordevice 60 can include first and second doped regions 64 and 66 and theintervening region 65 configured as a P⁺PN+ or a structure.

FIG. 6C is a graph showing dopant profiles along the section DD′ of FIG.6B. The profiles 67 a and 67 c represent p type and n type dopantprofiles of the first and second doped regions 64, 66, respectively. Inaddition, the profile 67 b is a p-type dopant profile of the substrate62.

The doped regions of the wear-out monitor device 60 of FIGS. 6A and 6Bare illustrated by way of example only, and other embodiments arepossible, where the first and second doped regions 64 and 66 arerespectively doped such that the first regions 64 is doped to form anyone of P⁺, P, P⁻, N⁺, N or N⁻ regions, while the second doped region 66is doped to form any one of P⁺, P, P⁻, N⁺, N or N⁻ regions that oppositein dopant type to the first doped region 64.

When the intervening region 65 is present between the first and seconddoped regions 64 and 66, any one of an N⁺NP structure, an N⁺N⁻P or anNIP structure, an NN⁻P structure, an NIP structure, a P⁺PN structure,P⁺P⁻N structure, a P⁺IN structure, a PP⁻N structure, or a PIN structurecan be formed.

As described herein and throughout the disclosure, a doped region cangenerally have a peak dopant concentration between about 1×10¹³ cm⁻³ andabout 1×10²² cm⁻³. In addition, heavily doped regions denoted as N⁺ orP⁺ regions can have a peak doping concentration exceeding about 1×10¹⁸cm⁻³ or about 1×10¹⁹ cm⁻³. In addition, lightly doped regions denoted asN⁻ or P⁻ regions can have a peak doping concentration lower than about1×10¹⁴ cm⁻³ or about 1×10¹³ cm⁻³.

In the wear-out monitor device 60 of FIG. 6A, the first doped region 64is formed by implanting dopants, e.g., p-type dopants, through anopening formed in the dielectric layer 63; however, embodiments are notso limited. For example, other masking (e.g., photoresist) and doping(e.g., diffusion) techniques may be used in lieu or in addition to usingthe dielectric layer 63 as an implantation mask.

Referring back to FIGS. 6A/6B, the wear-out monitor device 60additionally includes a first electrode 68 a and a second electrode 68 bcontacting the first doped region 64 and the second doped region 66,respectively, through openings in dielectric layer 63. In theillustrated embodiment, the first electrode 68 a comprises or is formedof the monitor atoms and serves as a reservoir of the monitor atoms. Thefirst electrode 68 a is configured such that, when the wear-out monitordevice is subjected to a set of predetermined conditions for apredetermined duration, some of the monitor atoms in the first electrode68 a diffuse into a depletion region formed between the first and seconddoped regions 64, 66. Depending on the concentration and/or depth of thediffused monitor atoms in the underlying semiconductor material, e.g.,in the depletion region, a cumulative wear-out history, e.g., acumulative thermal wear-out history, of the device 60 can be at leastindirectly determined.

By way of example, FIG. 6C is a graph 69 illustrating calculatedconcentration profiles of gold in a silicon device substrate of thewear-out monitor device in FIGS. 6A/6B, after diffusing at 125° C. forvarious times. In particular, the concentration profiles 67 d illustratepredicted concentration profiles of gold after diffusing for 1-10 yearsin at 125° C. By obtaining information regarding the depth and/orconcentration of dopants in a depletion region, and using the knowndiffusivity equations such as those in TABLE 1, a cumulative thermalhistory, or thermal wear-out level, can be obtained.

It will be appreciated that, according to embodiments, theconcentrations of dopants and the dimensions/configurations of the firstdoped region 64, the second doped region 66 and the intervening region65 are selected such that desired device attributes are obtained. Forexample, in the illustrated embodiment, because the intervening region65 is doped to a lower concentration compared to the second doped region66, a relatively larger depletion region is formed therein. When themonitor atoms diffuse into the depletion region, various electricalproperties of the depletion region can be made to determine,qualitatively and/or quantitatively, the relative concentration themonitor atoms in the depletion region, as discussed more in detailinfra. Thus, the depletion can serve as a monitor region for quantifyingthe amount of monitor atoms that may have diffused, from which acumulative thermal history can be determined.

Thus, as configured, the wear-out monitor device 60 of FIG. 6A/6B has areservoir of monitor atoms (e.g., first electrode 68 a) disposed on asurface of the substrate and a monitor region (e.g., depletion region inthe intervening layer 65) formed in the substrate. The monitor atomshave diffusion characteristics in the semiconductor material of thesubstrate such that when the wear-out monitor device is subjected to aset of predetermined stress conditions for a predetermined duration,some of the monitor atoms diffuse into the monitor region. The reservoircan include, e.g., an electrode containing the monitor atoms or a layerformed of the monitor atoms. The monitor region can include a region inthe substrate, e.g., a depletion region formed by a PN junction asdescribed above, for example.

Various embodiments of the wear-out monitor device including thewear-out monitor device 60 of FIGS. 6A/6B, are configured such that achange in a property, e.g., an electrical property, or an electricalsignature, associated with the presence of the monitor atoms in themonitor region can be measured. The electrical signature can be, forexample, any one or more of: junction leakage, junction capacitance,junction built-in potential, junction reverse recovery time, bipolarbase transit time (fT), metal-oxide-semiconductor (MOS) transistorthreshold voltage, MOS transistor subthreshold swing, MOS channelleakage, punch-through breakdown voltage (BV) and impact ionizationbreakdown voltage (BV), to name a few. Properties other than electricalproperties or signatures associated with the presence of the monitoratoms in the monitor region can alternatively or additionally bemeasured to determine wear out of a device. For example, changes in amagnetic property, an optical property, and/or one or more otherphysical properties can be detected. Furthermore, the changes in one ormore physical properties can be monitored on-chip and/or off-chip, e.g.,in a post-mortem failure analysis.

The set of predetermined stress conditions and a predetermined duration,which causes some of the monitor atoms to diffuse into the monitorregion can include, e.g., a temperature range between about 20° C. andabout 250° C., between about 50° C. and about 200° C. or between about75° C. and about 125° C.; an electric field, e.g., between 0.01 MV/cmand about 1000 MV/cm, between about 0.1 MV/cm and about 100 MV/cm, orbetween about 1 MV/cm and about 10 MV/cm; and a time duration, e.g.,between about 1 day and about 1000 years, between about 1 month andabout 100 years, or between about 1 year and 10 years. In someembodiments, the wear-out monitor device can be configured such that adistance between the surface on which the monitor atoms are disposed andthe monitor region can be any distance that is calculated to be adiffusion length, e.g., a distance at which the concentration decreasesto about 1/e of the peak surface concentration, based on a combinationof the predetermined conditions and the predetermined time duration.

Referring back to FIG. 2B, in some embodiments, some IC devices comprisea monitoring device and a reference device on the same semiconductorsubstrate. FIGS. 7A and 7B illustrate a wear-out monitor device 60 and areference device 70 according to such embodiments. The wear-out monitordevice 60 of FIG. 7A is similar or substantially identical to thewear-out monitor device 60 of FIGS. 6A/6B, except for relative positionsof the first electrode 68 a and first doped region 66 relative to thesecond electrode 68 b, whose alterations do not alter the operation ofthe wear-out monitor device 60, and therefore a detailed description ofthe wear-out monitor device 60 is omitted herein. The reference device70 of FIG. 7B is similar or substantially identical to the wear-outmonitor device 60 of FIG. 7A, except for the electrodes.

The reference device 70 includes first and second doped regions 64, 66that form a second PN junction, similar to the PN junction of thewear-out monitor device 60 described above with respect to FIGS. 6A/6B.The first electrode 78 a of the reference device 70 may be formed of amaterial that has different diffusion property than monitor atoms of thefirst electrode 68 a of FIG. 7A. Wear-out levels of a monitored devicein an IC can be determined using the difference in diffusion propertiesbetween the monitor atoms and the electrode material of the firstelectrode 78 a. Once fabricated, atoms of the first electrode 78 a ofthe reference device 70 do not diffuse substantially into the underlyingsemiconductor material under the conditions in which monitor atomsdiffuse in the monitor device 60 of FIG. 7A. For example, the firstelectrode 78 a of the reference device 70 can be formed of heavily dopedpoly silicon, tungsten, W, TiN, WN, TaN, TaCN, NiSi, WSi, etc., to namea few. That is, when the IC device including both the wear-out monitordevice 60 and the reference device 70 is subjected to a wear-out stress,the monitor atoms of the wear-out monitor device 60 have sufficientdiffusion length such that they diffuse into the underlyingsemiconductor material, e.g., into the depletion region formed in the PNjunction. In contrast, the atoms of the first electrode 78 a of thereference device 70 have a diffusion length that is negligible (e.g.,less than a few angstroms), such that the underlying semiconductormaterial is essentially free of the atoms of the first electrode 78 aafter the IC device is subjected to the wear-out stress.

Thus, in the illustrated embodiment of FIGS. 7A and 7B, the IC devicehas integrated therein the reference device 70 and the wear-out monitordevice 60 that are similar, e.g., essentially identical, except for thematerials of the respective first electrodes 78 a, 68 a. For example,each of the wear-out monitor device 60 and the reference device 70includes a PN junction such as a P⁺PN⁺ junction or an N⁺NP⁺ junction, inwhich a junction having formed therein a depletion region, from whichelectrical signals associated with monitor atoms diffused thereto can bedetected using various techniques, e.g. reverse bias leakage. However,other embodiments are possible. For example, the materials of therespective second electrodes 78 b, 68 b may be different instead of orin addition to the respective first electrodes 78 a, 68 a. For example,the second electrode 78 b may contain the monitor atoms instead of or inaddition to the first electrode 78 a.

As described above with respect to embodiments of FIGS. 2A and 2B, themonitor atoms, while being configured to diffuse into the underlyingsemiconductor material, may also be integrated in the same substrate ofan IC that also has a core circuit and/or a reference device, accordingto some embodiments. However, without proper precaution, the monitoratoms can undesirably diffuse from the wear-out monitor device to otherparts of the IC, such as to the core circuit and/or to the referencedevice. In addition, some monitor atoms may diffuse faster than theirexpected velocities based on bulk diffusivities, due to the presence ofcrystal imperfections such as grain boundaries, dislocations orinterfaces. However, many monitor atoms are known to severely degradesemiconductor devices. For example, many metals that may be goodcandidates for monitor atoms, e.g., gold and copper, are known to formwhat are known as mid-gap or deep level traps in silicon. Mid-gapcenters or deep level traps occupy energy states near the middle of theband gap of the semiconductor material. In operation, when excessminority carriers, e.g., electrons in a p-type semiconductor region orholes in an n-type semiconductor region, are created in a semiconductordevice in the core circuit, the mid-gap centers created by theunintended presence of monitor atoms can detrimentally affect the deviceperformance by, among other things, degrading minority carrier lifetimesand increasing leakage. In addition, the presence of monitor atoms inthe reference device may defeat its purpose as a reference device. Thus,in various embodiments, it may be desirable to block the diffusion ofthe monitor atoms such that they do not detrimentally affectsemiconductor devices outside of the wear-out monitor device.

Referring to 6A/6B and 7A/7B, to limit undesirable diffusion of monitoratoms from the wear-out monitor devices to other parts of the IC device,each of the wear-out monitor device 60 and the reference device 70 mayhave, laterally on one or both sides, isolation regions 61 a, e.g.,shallow trench isolation regions. In addition, each of the wear-outmonitor device 60 and the reference device 70 may have a buriedisolation region 61 b, e.g., a buried oxide (BOX) of asilicon-on-insulator (SOI), laterally extending between adjacentisolation regions 61 a such that an isolation tub formed of theisolation regions 61 a and 61 b encloses the first and second dopedregions 64 and 66 and the intervening region 65. The isolation tub isconfigured to prevent unintended lateral and vertical diffusion ofmonitor atoms from the wear-out monitor device 60 into other parts ofthe IC device, including, e.g., the reference device 70 and/or devicesin the core circuitry (not shown for clarity, see FIGS. 2A/2B) formed inthe same substrate.

As described above with respect to FIGS. 2A and 2B, the IC devicesaccording to embodiments include a sensing circuit for sensing anelectrical signature associated with atoms of the monitor atoms anddetermine therefrom a cumulative history of wear-out stresses, e.g.,thermal or electrical wear-out stresses, that the IC device may havebeen subjected to. For example, for each of the wear-out monitor device60 and the reference device described with respect to FIGS. 6A/6B and7A/7B, a reverse bias may be applied between the first electrodes 68 a,78 a and the second electrode 68 b, 78 b, such that a reverse biasleakage can be measured across the PN junction. By comparing the reversebias currents between the wear-out monitor device 60 and the referencedevice 70, which may be proportional to the concentration of impurityatoms in the respective depletion regions, a determination of the degreeof wear-out of monitored devices in the core circuitry can bedetermined.

Referring to FIG. 8, a wear-out monitor device 80 according to someother embodiments is illustrated. Structural features of the wear-outmonitor device 80 are similar to corresponding features of the wear-outmonitor device 60 of FIG. 6A/6B, and therefore a detailed description isomitted herein. The wear-out monitor device 80 is configured as acurrent monitor for monitoring, e.g., the degree of wear-out related tocumulative current passed through a monitored structure in the corecircuitry (not shown for clarity, see FIGS. 2A/2B), which may be asimilar device in the core circuitry. By placing the monitor structurein electrical series with the monitored structure, for example, thecumulative current passed through the monitored structure can bemonitored. In the illustrated embodiment, the current is monitoredindirectly by measuring the effect of diffusion rate of the monitoratoms caused by Joule-heating of the wear-out monitor device. Inoperation, the PN junction of the wear-out monitor device 80 isforward-biased in series with the monitored structure for repeatedgeneration of current-based wear-out stress. In FIG. 8, the region inwhich Joule-heating occurs is represented as a resistor formed in serieswith the forward-biased PN junction between a first electrode 68 acontaining the diffusing material (e.g., Au) and a second electrode 68b. In response to the forward bias, the series resistor of the monitorstructure generates the heat which causes the monitor atoms in the firstelectrode 68 a to diffuse into the underlying substrate, e.g., adepletion region formed in the PN junction. While not shown, the IC mayinclude a reference device (not shown for clarity, see FIG. 2B) similarto the reference device 70 of FIG. 7B, which is does not have monitoringatoms. Alternatively, a reference device may be similar or substantiallyidentical to the wear-out monitor device 80 except that it notconfigured to receive the forward current-based wear-out stress.Subsequently, by comparing reverse bias currents between the wear-outmonitor device 80 and the reference device, the wear-out state of themonitored structure can be determined therefrom, in a similar manner asdescribed above.

Referring to FIG. 9, a wear-out monitor device 90 according to someother embodiments is illustrated. The wear-out monitor device 90 isconfigured as a voltage monitor or electric field monitor formonitoring, e.g., cumulative electric field-based wear-out stressapplied to a monitored device in the core circuitry (not shown forclarity, see FIGS. 2A/2B). Structural features of the wear-out monitordevice 90 are similar to corresponding features of the wear-out monitordevice 60 of FIG. 6A/6B, and therefore a detailed description is omittedherein. The wear-out monitor device 90 is configured to bereverse-biased and electrically connected, e.g., electrically inparallel, with the monitored device to receive repeated electricfield-based wear-out stress from electric field generated by thereverse-biased PN junction. In response to the electric field-basedwear-out stress, the monitored impurity atoms, e.g., charged impurityatoms, may be caused to diffuse into a monitored region, e.g., thedepletion region of the reverse biased PN junction. The IC device mayinclude a reference device (not shown for clarity, see FIGS. 2A/2B)similar to the reference device 70 of FIG. 7B, which does not havemonitoring atoms that diffuse. Alternatively, a reference device may besubstantially identical to the wear-out monitor device 90 except that itnot configured to receive the electric field wear-out stress caused bythe reverse biased PN junction. Subsequently, by comparing reverse biascurrents between the wear-out monitor device 90 and the referencedevice, the wear-out state of the monitored structure can be determinedtherefrom.

Referring to FIGS. 10A and 10B, a wear-out monitor device 100 a/100 bconfigured for monitoring the wear out level of a PN junction isillustrated. FIGS. 10A and 10B represent the wear-out monitor deviceprior to (100 a) and subsequent to (100 b) being subjected tousage-related wear-out stress, e.g., repeated wear-out stress. Thewear-out monitor device 100 a/100 b comprises a first doped region 102a/102 b doped with a first dopant type, e.g., a donor, to aconcentration N_(d), and a second doped region 104 a/104 b doped with asecond dopant type, e.g., an acceptor, to a concentration N_(a). Thesecond doped region 104 a/104 b comprises monitor atoms, where themonitor atoms are configured to diffuse into the underlyingsemiconductor material, e.g., into the depletion region of the PNjunction. In some embodiments, the monitor atoms may be present inaddition to the acceptor atoms having the concentration N_(a). In otherembodiments, the monitor atoms may serve as acceptor atoms such that theacceptor atoms having the concentration N_(a) may at least in part bethe monitor atoms. In other embodiments, the monitor atoms may bepresent as part of an electrode layer, as described above with respectto FIGS. 6A/6B. As described above, a wear-out stress causes a change ina rate at which the monitor atoms diffuse into the underlyingsemiconductor material. An initial schematic concentration profile 106 athrough a section DD′ of the initial wear-out monitor device 100 a showsa relatively abrupt concentration profile of N_(a) in a verticaldirection (x). The wear-out monitor device 100 a may be subjected to awear-out stress, e.g., thermal wear-out stress as described in FIG.6A-6C, in forward bias as described in FIG. 8, and/or reverse bias asdescribed in FIG. 9. After being subjected to the wear-out stresses, theschematic concentration profile 106 b through a section DD′ of thecycled wear-out monitor device 100 b shows a relatively diffuseconcentration profile of N_(a) in a vertical direction (x). By comparingthe electrical signatures (e.g., reverse bias leakage) associated withthe concentration profiles 106 a and 106 b, the wear-out state of themonitored structure 106 b may be determined.

FIGS. 11A and 11B illustrate a wear-out monitor device 110 a/110 bconfigured for monitoring punch-through characteristics between adjacentheavily doped regions. As described herein, a punch-through effectrefers to a phenomenon in which depletion regions of two separated butadjacent heavily doped regions merge. For example, in ametal-oxide-semiconductor (MOS) transistor, a punch-through effectbetween a source and a drain causes a rapid increase in channel currentwith increasing drain-source voltage, which can be undesirable becausethe voltage at which the punch-through occurs may limit the operatingvoltage of the IC device. FIGS. 11A and 11B represent the wear-outmonitor device prior to (110 a) and subsequent to (110 b) beingsubjected to a usage-related wear-out stress. The wear-out monitordevice 110 a/110 b comprises a first heavily doped region 116 a/116 b,which may be a buried doped region, that is doped with a first dopanttype, e.g., a donor, to a concentration N_(d), and a second heavilydoped region 114 a/114 b doped with a second dopant type, e.g., anacceptor, to a concentration N_(a). In some embodiments, the monitoratoms may be present in addition to the acceptor atoms having theconcentration N_(a). In other embodiments, the monitor atoms may serveas acceptor atoms, such that the acceptor atoms having the concentrationN_(a) may at least in part be the monitor atoms. In other embodiments,the monitor atoms may be present as part an electrode layer, asdescribed above with respect to FIGS. 6A/6B. After repeated cycling ofthe monitor structure, e.g., by repeatedly reverse-biasing the firstheavily doped region 116 a/116 b and the second heavily doped region 114a/114 b, the effective width between the first heavily doped region 116a/116 b and the second heavily doped region 114 a/114 b reduces from Wto W′ as illustrated, and the associated electrical signatures (e.g.,punch-through voltage) may be used to determine therefrom a wear-outstate of a monitored device in the core circuitry.

Referring to FIG. 12, a wear-out monitor device 120 a/120 b similar tothe wear-out monitor device 110 a/110 b of FIGS. 11A and 11B andconfigured for monitoring punch-through characteristics between adjacentheavily doped regions is illustrated. However, in contrast to thewear-out monitor device 110 a/110 b of FIGS. 11A/11B, a first heavilydoped region 124 a/126 a and a second heavily doped region 124 b/126 bare laterally separated instead of being vertically separated. Monitoratoms may be present in one or both of the first and second heavilydoped regions 124 a, 124 b in a similar manner as described above withrespect to the second heavily doped region 114 a/114 b of FIGS. 11A and11B. FIG. 12 represents the wear-out monitor device prior to (120 a) andsubsequent to (120 b) being subjected to the usage-related wear-outstress in an analogous manner as described above with respect to FIGS.11A and 11B. In an analogous manner as described above with respect toFIGS. 11A and 11B, the effective width between the first heavily dopedregion 124 a/126 a and the second heavily doped region 124 b/126 breduces from W to W′ as illustrated, and the associated electricalsignatures (e.g., punch-through voltage) may be used to determinetherefrom a wear-out state of a monitored structure.

Referring to FIGS. 13A and 13B, a wear-out monitor device 130 a/130 bconfigured for monitoring channel degradation ofmetal-oxide-semiconductor (MOS) transistors is illustrated, according toembodiments. The wear-out monitor device 130 a/130 b comprises a source132 and a drain 134 formed in a semiconductor substrate 132. Thewear-out monitor device 130 a/130 b additionally comprises a gatedielectric 135 and a gate 136 a/136 b. FIGS. 13A and 13B represent thewear-out monitor device prior to (130 a) and subsequent to (130 b) beingsubjected to a usage-related wear-out stress. The wear-out monitordevice 130 a/130 b can be used to monitor, e.g., usage-related wear of amonitored device (not shown for clarity, see FIG. 2B), which may be asimilarly configured MOS transistor in the core circuit. In the wear-outmonitor device 130 a/130 b, the monitor atoms may be disposed on any oneof the source 132, the drain 134 or the gate 136 a/136 b of the wear-outmonitor device 130 a/130 b configured as a MOS transistor. Aftersubjecting to a wear-stress, e.g., a thermal stress or repeated cyclingof the wear-out monitor device 130 a/130 b in a similar manner as themonitored structure, the level of wear-out of the monitored device maybe determined. For example, by comparing the wear-out monitor device 130b that has been subjected to the wear-out stress to a reference device(not shown for clarity, see FIG. 2B), which may be another monitorstructure that has not gone through the wear-out stress, the associatedelectrical signatures may be used to determine therefrom a wear-outstate of a monitored structure 130 a/130 b. For example, the monitoratoms may diffuse into an initial channel region 138 a of FIG. 13A toform a diffused channel region 138 b of FIG. 13B. Such degradation canbe detected, e.g., by measuring transistor parameters such as acurrent-voltage measurements.

Referring to FIGS. 14A-14B, a method of manufacturing a wear-out monitordevice is illustrated, according to some embodiments. In particular, themethod relates to forming the reservoir of monitor atoms. It will beappreciated that directly contacting a layer of monitor atoms such as alayer of gold can result in defects, such as poor contact and/ordelamination due to poor adhesion. Without being bound to any theory,such defects may be caused by a relatively high interfacial energybetween some diffusing material and the semiconductor substrate. Inorder to create a reservoir of such impurity atoms without such defects,a mixture layer having the diffusing material may be formed, instead ofa pure layer of the diffusing material. The mixture may be an alloylayer, a compound, a doped layer or a mechanical mixture, among otherforms of mixture.

By way of example, an intermediate monitor structure 140 a is shown inFIG. 14A, which includes a substrate 142 in which a first doped region144 and a second doped region 146 interposed by an intervening region145 are formed, similar to the monitor structures described above withrespect to FIGS. 6A/6B. Unlike FIGS. 6A/6B, instead of forming a layerof monitor atoms, e.g., gold atoms, directly on the surface of the firstdoped region, an adhesion layer 149, such as a polysilicon layer, may beformed between a layer 148 a of monitor atoms and the underlyingsemiconductor material of the first doped region 144. Subsequently, theintermediate monitor structure 140 a may be subjected to a thermalanneal, resulting in a wear-out monitor device 140 b having an adhesionlayer, e.g., a polysilicon layer, that is impregnated or at leastpartially saturated with the monitor atoms, e.g., gold. An electrode 148b serving as a reservoir of monitor atoms is thus formed, with improvedadhesion properties with the underlying silicon, compared to a purelayer of the monitor atoms. Other embodiments are possible, e.g., amixture layer of gold and polysilicon can be formed directly on thesilicon surface, or another material such as a dielectric material or achalcogenide material that can hold a relatively high concentration ofgold with good adhesion properties can be used as the intervening layer149. It will be appreciated that the specific combination of theintervening layer and the method of forming can depend on the type andconcentration of the specific wear-out diffusing material that is to beused.

Referring to FIGS. 15A-15D, various configurations 150 a-150 d of awear-out monitor device including a PN junction are illustrated,according to embodiments. In each of the configurations 150 a-150 d, aPN junction may be formed in a substrate 152. A first doped region 154a-154 d doped with a first dopant type contacts the first electrode 158a-158 d serving as reservoirs of monitor atoms, while a second dopedregion doped with a second dopant type is formed in variousconfigurations. In the configurations 150 a-150 d, the second dopedregion is configured as the substrate 152 (FIG. 15A), a well 155 b (FIG.15B) formed in a substrate 152, a buried collector region 156 c formedin the substrate 152 (FIG. 15C) and a buried collector region 156 dformed in a well 155 formed in the substrate 152 (FIG. 15D). It will beappreciated that dopant concentrations of the first and second dopedregions can be varied to tailor the characteristics of the monitorregion, e.g., to tailor the dimensions of the depletion region formedtherein and/or to tailor the built-in voltage, among othercharacteristics, as described supra. For example, where a relativelylarge depletion region is desired, the doped region contacting thereservoir may be doped heavily, while the doped region not contactingthe reservoir may be doped relatively lightly.

Referring FIGS. 16A-16D, various configurations of a wear-out monitordevice are illustrated, in which the flux or the diffusion rate ofmonitor atoms diffusing into the underlying substrate are controlled byphysically limiting access to the substrate, according to embodiments.Referring to FIG. 16A, the area (represented by the width) of contactbetween the first electrode 168 a serving as the reservoir of monitoratoms and the first doped region 164 a may be restricted by restrictingthe size of the opening through the dielectric mask 163 formed over thesubstrate, thereby limiting the diffusion of the monitor atoms into thesubstrate. Referring to FIG. 16B, in addition to restricting the size ofthe openings through the dielectric mask 163, the number of openings canbe further increased or decreased as needed. Referring to FIG. 16C, thearea of contact between the first electrode can be further reduced byforming additional diffusion-blocking layers 165, e.g., nitride layers,in the openings formed between or though field oxide regions. Referringto FIGS. 16D-16E, the flux of monitor atoms available for diffusion intothe underlying substrate can be further restricted using an adhesionlayer 169 d-169 g under the first electrodes 168 a-168 d that serve asthe reservoir of monitor atoms. The wear-out monitor devices 160 d, 160e and 160 f of FIGS. 16D, 16E and 16F are substantially identical to thewear-out monitor devices 160 a, 160 b and 160 c of FIGS. 16A, 16B and16C, respectively, except for the presence of the adhesion layers 169d-169 f, which can be formed of, e.g., a polysilicon, and interposedbetween the respective first electrodes 168 a, 168 b, and 168 c and therespective first doped regions 164 a, 164 b and 164 c. Referring to FIG.16G, the area of contact between the first electrode 168 c and the firstdoped region 164 c can be further reduced by forming spacers 167, e.g.,nitride spacers layers, in the openings formed though the additionaldiffusion-blocking layers 165.

Referring to FIGS. 17A and 17B, wear-out monitor devices 170 a and 170 bconfigured as bipolar junction transistors (BJTs) are illustrated,according to embodiments. A first doped region 174 doped with a firstdopant type, which is contacted by a first electrode 178 a serving as areservoir of impurity atoms, may be formed at a surface region andconfigured as an emitter of a BJT. A second doped region 175 doped witha second dopant type opposite the first dopant type, which is contactedby a second electrode 178 b, may serve as a base of the BJT. Third dopedregions 176 a and 176 b doped with the first dopant type, which arecontacted by the third electrodes 178 c, may serve as a collector of theBJT. In FIG. 17A, the collector region is formed of a deep well, whilein FIG. 17B, the collector region is formed of a buried collectorregion. In addition, in FIG. 17B, the buried region doped with the firstdopant type can be formed below the well doped with the second dopanttype, thereby forming a base/collector junction of the BJT. Thus formedBJT can be configured for monitoring wear-out resulting from variousstresses including thermal, current and/or voltage stresses.

Referring to FIGS. 18A-18D, wear-out monitor devices 180 a-180 dconfigured as MOS transistors are illustrated, according to embodimentsfor monitoring wear-out of a monitored structure in a core circuitry(not shown for clarity, see FIGS. 2A/2B), which may be a similarlyconfigured MOS transistor elsewhere on the same substrate, e.g., in thecore circuitry. Each of the wear-out monitor devices 180 a-180 dcomprises a source 182 and a drain 184 formed in a semiconductorsubstrate 182. Each of the wear-out monitor devices 180 a-180 dadditionally comprises a gate dielectric 185 and a gate 186 a-186 d.Each of the wear-out monitor devices 180 a-180 d has a differentconfiguration for disposing the reservoir of monitor atoms. For example,the monitor atoms may be disposed as a separate layer 189 a, e.g., apolysilicon layer, over a gate 186 a (FIG. 18A), as a separate layer 189b (FIG. 18B), e.g., a buried oxide doped with the diffusing material,over a gate 186 b, or on one or both of the source 182 and the drain184, either as a layer 187 c of monitor atoms directly on thesource/drain 182/184 (FIG. 18C), or as reservoir layers 187 d doped withthe monitor atoms formed on the source/drain 182/184 (FIG. 18D). Whendisposed on or as part of the gate 186 a/186 b, the wear-out monitordevices 180 a/180 b may be used to monitor various wear-out mechanismsrelated to degradation in threshold voltage, subthreshold slope,interfacial charge, gate dielectric (e.g., time-dependent dielectricbreakdown), off state leakage, on/off ratio, hot channel injection, etc.When disposed on or as part of one or both of the source 182 and thedrain 184, the wear-out monitor devices 180 c/180 d may be used tomonitor punch-through, short-channel effect, junction capacitance, etc.

Referring FIG. 19A, a wear-out monitor device 190 a configured forsensing impedance as an indicator of the state of wear-out isillustrated, according to embodiments. The wear-out monitor device 190 aincludes a substrate 198 having formed therein a monitor structure 194 aand a reference structure 192 that are commonly connected to a firstterminal T1. The reference structure 192 is further connected to asecond terminal T2 and has an impurity region 193 doped with monitoratoms. The monitor structure 194 a is further connected to a thirdterminal T3 and has an impurity region 196 a doped with the same monitoratoms as the impurity region 193 of the reference structure 192. Whilethe impurity region 193 of the reference structure 192 is enclosed by adiffusion barrier structure 195, no such enclosure exists for themonitor structure 194. In some embodiments, the impurity region 193 andthe impurity region 193 have the same or similar concentration profileof monitor atoms. Upon receiving a wear-out stress, e.g., a thermalwear-out stress, the impurity region 196 a of the monitor structure 194a would have a lower concentration of the monitor atoms compared to aninitial concentration and compared to the impurity region 196 a of themonitor structure 194 a, due to free diffusion of the monitor atoms inthe impurity region 196 a compared to limited diffusion of the monitoratoms in the impurity region 193. In contrast, the impurity region 192of the reference structure 192 would have a relatively unchangedconcentration of the impurity atoms. The degree of wear-out of amonitored device in a core circuitry (not shown for clarity, see FIGS.2A/2B) can be measured based on the resulting changes in impedancemeasurements, which can resolve relatively small changes inconcentration of the monitor impurity atoms at small time scales and/orlower temperatures, thereby making the wear-out monitor device 190 aparticularly suitable for shelf-life applications. FIG. 19B illustratesa graph 191 schematically illustrating time evolutions of the impedanceZ_(a) of the reference structure 192 measured between T1 and T2 and thevarying impedance Z_(b)(t) of the monitor structure 196 a measuredbetween T1 and T3. As illustrated, the Za changes by a relatively smalldegree after receiving the wear stress, while the Z_(b)(t) changes by arelatively large degree as illustrated. Based on the time evolution ofthe Z_(b)(t), the wear-out state of the monitored device in the corecircuitry can be determined.

Referring FIG. 19C, a wear-out monitor device 190 c configured forsensing impedance as an indicator of the state of wear-out isillustrated, according to embodiments. The wear-out monitor device 190 cis substantially identical to the wear-out monitor device 190 a of FIG.19A except, in the wear-out monitor device 190 c, an impurity region 196b of a monitor structure 194 a is partially enclosed by a partialdiffusion barrier structure 197. The partial diffusion barrier structure197 has an opening such that diffusion of the monitor atoms out of theimpurity region 196 b is partially restricted. Such configuration can bebeneficial when the expected diffusion of the monitor atoms isrelatively rapid, to prevent too rapid of a change in concentration ofthe monitor atoms, or in the Z_(b)(t).

Referring FIG. 19D, a wear-out monitor device 190 d configured forsensing impedance as an indicator of the state of wear-out isillustrated, according to embodiments. Unlike the wear-out monitordevices 190 a of FIG. 19A and 190 c of FIG. 19C, the wear-out monitordevice 190 d does not have a monitor structure and a reference structurethat are discrete. Instead, the wear-out monitor device 190 d has amonitor region 194 d and reference region 192 d that are enclosed by abarrier structure 195 d, such the monitor atoms in the reference region192 d are configured to laterally diffuse into the monitor region 194 d.

It will be appreciated that the wear-out monitor devices 190 a, 190 band 190 d can be advantageous, among other reasons, because asemiconductor junction is not needed for impedance measurement-baseddetermination of the wear-out level. As a result, the material of thesubstrate 198 can be any suitable diffusing medium, including aninsulator (e.g., SiO2, sapphire) or any semiconductor substratedisclosed herein. Thus, an additional degree of freedom, i.e., thediffusing medium, is available for designing the monitor device. Inaddition, because the monitor atoms are prevented from freely diffusingaway at least from the reference region, relatively small amount ofmonitor atoms may be needed.

Sensing Circuitry for Wear-Out Monitors

In the following, various circuitry that can be included in the sensingcircuitry for sensing the various electrical signatures associated withthe wear-out monitor devices and the reference devices according toembodiments are described. It will be appreciated that each of thevarious circuitry disclosed herein can be part of the sensing circuit 25a/25 b described above with respect to FIGS. 2A/2B.

FIGS. 20A-21B illustrate various conversion circuits configured forconverting measured input signals from wear-out and/or reference monitordevices described herein into output signals, according to variousembodiments.

FIG. 20A illustrates a punch-through wear-out monitor conversion circuit200 a configured for conversion of monitor signals from various monitordevices and reference devices described above, according to embodiments.In particular, the conversion circuit 200 a may be configured formonitoring punch-through characteristics of semiconductor devices. Forexample, the conversion circuit 200 a may be electrically connected towear-out monitor devices configured for monitoring punch-throughcharacteristics described above, e.g., with respect to FIGS. 11A-11B and12A-12B. The conversion circuit 200 a is configured such that, below apredetermined punch-through voltage, no current flows through apunch-through monitor device 202. When no current flows through thepunch-through the device 202, potentials of the + and − terminals of acomparator 204 are equal. Once a punch-through occurs, the comparator204 is activated, and a current flows through the punch-through device202. The punch-through voltage is output through a DAC 206, which may berecorded.

FIG. 20B illustrates a threshold voltage (Vth) wear-out monitorconversion circuit 200 b configured for conversion of monitor signalsfrom various monitor devices and reference devices described above,according to embodiments. In particular, the conversion circuit 200 bmay be configured for monitoring Vth variation characteristics of MOSdevices. In operation, the current source 201 b raises the voltage on aVT node 207 (ADC input) until the voltage saturates. If a constantcurrent is output from the current source 201 b, the saturation involtage at the VT node 207 varies according to the variation of Vth ofthe transistor 208. The Vth voltage is output to ADC 205 b and recordedover time.

FIG. 20C illustrates a diode forward voltage wear-out monitor conversioncircuit 200 c configured for conversion of monitor signals from variousmonitor devices and reference devices described above, according toembodiments. In particular, the conversion circuit 200 c may beconfigured for monitoring forward voltages of diodes. In operation, thecurrent from current source 201 c raises the voltage on a node 207 (ADCinput) until the voltage saturates. If a constant current is output fromthe current source 201 c, the saturation voltage at the node 207 willvary with of forward voltage of the diode 203, which can be output toADC 205 c and recorded over time.

FIG. 21A illustrates a conversion circuit 210 a configured forconversion of monitor signals from various monitor devices and referencedevices described above, according to some embodiments. In operation, ina first stage, the conversion circuit 210 a is configured to monitor avoltage on a wear-out monitor 212 a at a node 214 a. This is achievedby, in a first stage, buffering the voltage of a wear-out monitor device212 a at the node 214 a using a first amplifier 216 and a first resistorR1. In a second stage, the buffered voltage at a node 217 issubsequently gained up by a second amplifier 218 a, and subsequentlyconverted for output at an ADC 219 a.

FIG. 21B illustrates a conversion circuit 210 b configured forconversion of monitor signals from various monitor devices and referencedevices described above, according to some embodiments. In operation, ina first stage, the conversion circuit 210 b is configured to monitor avoltage on a wear-out monitor 212 b at a node 214 b by first lowpass-filtering the input signal, followed by gaining using a firstamplifier 218 a, and subsequently converting for output at ADC 219.

FIG. 22A illustrates a capacitive programmable gain amplifier (PGA)circuit 220 a configured to compare output signals between a wear-outmonitor device 221 a and a reference device 221 b, according toembodiments. The PGA circuit 220 a includes two current sources 222 aand 222 b configured to supply currents to a wear-out monitor 221 a anda reference device 221 b, respectively. The PGA circuit 220 a furtherincludes two fully differential voltage-mode capacitive amplifiers 224and 226 connected to each of the wear-out monitor device 221 a and thereference device 221 b. As illustrated, the PGA circuit 220 a isconfigured as a chopped capacitive PGA with an output filter and abuffer, and is particularly adapted for amplifying small signaldifferences (˜tens to hundreds of nV) between outputs of the wear-outmonitor device 221 a and the reference device 221 b.

FIG. 22B illustrates a capacitive programmable gain amplifier (PGA)circuit 220 b configured to compare output signals between a wear-outmonitor device 221 c comprising a diode, and a reference device 221 dcomprising a diode, according to embodiments. Unlike the PGA circuit 220a of FIG. 22A, in the PGA circuit 220 b, the wear-out monitor device 221c and reference device 221 d are each connected to a common referencevoltage, Vref. Similar to the PGA circuit 220 a of FIG. 22A, the PGAcircuit 220 b is configured as a chopped capacitive PGA with an outputfilter and a buffer, and is particularly adapted for amplifying smallsignal differences (˜nV˜100 nV) between outputs of a wear-out monitordevice 221 c and a reference device 221 d.

FIG. 22C illustrates a current-to-digital ADC conversion circuit 220 cconfigured to compare output signals between a wear-out monitor device221 e comprising a diode and a reference device comprising a diode,according to embodiments. For illustrative purposes, in the illustratedembodiment, the ADC conversion circuit 220 c is a 128-channel,current-to-digital, analog-to-digital converter (ADC). The ADCconversion circuit 220 c includes 128 low power, low noise, low inputcurrent integrators, simultaneous sample-and-holds, and two high-speed,high-resolution ADCs with configurable sampling rate and resolutions upto 24 bits. The converted channel results are output on a single LVDSself-clocked serial interface, which reduces external hardware. AnSPI-compatible serial interface allows configuration of the ADC usingthe SDI input. The SDO output allows the user to daisy-chain severalADCs on a single, 3-wire bus. The ADC circuit 220 c can use the separatesupply IOVDD to reduce digital noise effect on the conversions.

FIGS. 23A-23C illustrate trans-impedance amplifiers (TIAs) 230 a-230 c,respectively, each configured to amplify and to convert current outputof monitor signals from various wear-out monitor devices or referencedevices described herein to a voltage signal, according to embodiments.In some embodiments, the TIAs can be used where a wear-out monitor has acurrent response that is more linear than the voltage response. Forexample, the illustrated TIAs 230 a-230 c can be used with a wear-outmonitor 234 which include a diode, e.g., a photodiode, where the currentresponse may have better than, e.g., 1% linearity over a wide range oflight input. The TIAs 230 a-230 c present low impedance to the wear-outmonitor 234 and isolate it from the output voltage of the operationalamplifier. Each of the TIAs 230 a-230 c has an amplifier 232 in aninverting configuration and a feedback resistor, R_(F), which sets thegain of the amplifier 232, whose value is −R_(F). The output each ofTIAs 230 a-230 c can be converted by an ADC. Each of the TIAs 230 a-230c is particularly suitable for converting low-level current of awear-out monitor to a voltage, as described infra.

Referring to FIG. 23A, in operation, the wear-out monitor device 234 isconnected between ground and the inverting input of the amplifier 232.The non-inverting input of the amplifier 232 is also connected toground. This provides a low impedance load for the wear-out monitordevice 234, which keeps the bias low. The high gain of the amplifier 232keeps the current through the wear-out monitor device 234 equal to thefeedback current through R_(F).

Referring to FIG. 23B, the TIA 230 b is similar to the TIA 230 a of FIG.23A, except, the TIA 230 b includes a DC supply V₁, e.g., a battery,between the wear-out monitor device 234 and ground, such that a wear-outmonitor can be measured with a positive output voltage. For example, ifa reverse bias leakage current (I_(D)) through a wear-out monitor device234 having a diode is 5 nA, and R_(F) is 1 MΩ, and V_(bias) is =−0.1V,V_(out)=5 nA*1MΩ=5 mV.

Referring to FIG. 23C, the TIA 230 c is similar to the TIA 230 a of FIG.23A, except, the TIA 230 c includes a DC supply V₂, e.g., a battery,having a V_(bias) between the non-inverting input of the amplifier 232and ground, such that a wear-out monitor can be measured with a positiveoutput voltage. For example, if a reverse bias leakage current through awear-out monitor device 234 having a diode is 5 nA, and R_(F) is 1 MΩ,and V_(bias) is =+0.1V, V_(out)=(5 nA*1MΩ)+0.1V=105 mV.

Thus, the trans-impedance amplifiers (TIAs) 230 a-230 c have inputoffset voltage due to the monitor device 234 that is very low while thegain is very high, such that they allow for very low input bias current(˜+/−20 fA) to be measured and amplified.

FIG. 24 illustrates a trans-impedance amplifier (TIA) 240 with anodebias multiplexed such that the TIA amplifier 240 is configured toamplify and to convert current outputs (I_(D1), I_(D2)) of monitorsignals from both a monitor device 234 and a reference device 236 intovoltage outputs, according to some embodiments. Advantageously, sincethe monitor device 234 and the reference device 235 use the sameV_(bias) and the same amplifier 232, errors in conversion of the currentoutputs (I_(D1), I_(D2)) are cancelled. In operation, the TIA 240 can bepart of the front end of a sensing circuit. The output from each devicecan be converted by an ADC whose result can be stored, and subsequentlysubtracted to calculate a difference in leakage current, for example.Storing the difference in leakage current over time would track, e.g.,the temperature the wear-out monitor device was exposed to over time.

Lifetime Indicator Systems

FIG. 25 illustrates a lifetime indicator system 250 having one or morewear-out monitor devices, according to embodiments. It will beappreciated that the lifetime indicator system 250 disclosed herein canbe part of the sensing circuit 25 a/25 b described above with respect toFIGS. 2A/2B.

The plurality of different monitor devices 252 a, 252 b, can bedifferent types wear out monitor devices formed in a common platform(e.g., a single chip or a single substrate), according to embodiments.The one or more different monitor devices 252 a, 252 b can provide,e.g., parallel and/or simultaneous monitoring data of different types ofwear-out stresses. In the illustrated embodiment, the one or morewear-out monitor devices include a temperature wear-out monitor 252 band a voltage or current wear-out monitor 252 a. In operation, the oneor more wear-out devices 252 a, 252 b can provide parallel and/orsimultaneous monitoring data to a respective ADC 254 a, 254 b, whoseoutput can be fed into a common processor 256. Simultaneously,respective limit alerts 257 a, 257 b can be generated based on themonitoring data from each of the one or more wear-out devices 252 a, 252b. Each limit alert 257 a, 257 b can be pre-established based onindividual minimum and maximum values limits placed by the user forrespective monitors. The lifetime indicator system 250 can also includea timer 255. The processor 256 is configured to receive the monitoringdata from each of the wear-out monitor devices 250 a, 250 b and todetermine, either based on information from an individual wear-outmonitor device 252 a or 252 b, or by combining information from the morethan one monitor devices 252 a, 252 b, a wear level of a relevant corecircuit device (not shown for clarity, see FIGS. 2A/2B) in a corecircuitry. Thus, calculated wear-out level may be stored in a memorydevice 258, e.g., a nonvolatile memory device. In some implementations,the calculated wear-out level data stored in the memory device can betransmitted in an encrypted form for protection.

In some embodiments, the lifetime indicator system 250 can be configuredas a supply current wear-out monitoring system. Many IC failures arecaused by wear-out of supply current modules, such as supply currentmodules configured for providing standby or power-save currents.Failures can occur when the supply current degrades due to wear-outcaused by EOS, ESD, corrosion and latent defects to name a few. Whenconfigured as a supply current wear-out monitoring system, the wear-outmonitor 252 a can be configured as a supply current wear-out monitor.When a failure does occur, by monitoring time-stamped supply currentvalues and recording them in the memory 258, and “playing back” suchcurrent values leading up to failure, information related to the causeof the failure can be obtained.

In other embodiments, the lifetime indicator system 250 can beconfigured as a device failure monitoring system, e.g., a transistordevice wear-out monitoring system for monitoring device failures thatdepend on voltage, current, temperature, and/or time. Examples of suchwear out mechanisms include wear-out due to hot carrier injection (HCI)and negative bias temperature instability (NBTI), which are known tonegatively affect transistor performance (speed and voltage). Accuracyof wear-out models for failures resulting from such mechanisms can beimproved by simultaneously monitoring a cumulative voltage stress on thetransistor, while also monitoring the temperature at which the voltagestress is applied.

Mission Profile Monitoring Systems

A mission profile generally describes loads and stresses acting on anitem, e.g., a component, a device or a system in actual use. As usedherein, a mission profile refers to a time-phased description of eventsand environments the item experiences from initiation to completion of aspecified mission for a specified time. The events and environments,e.g., loads and stresses, include, for example, changes in temperature,temperature profile, humidity, vibration, electric/magnetic fields, or acombination of these factors, among other environmental factors. It canbe important to specify the relevant stresses in their nature, intensityand duration of exposure, as well as the mix as closely as possible.With these details it is possible, within specified accuracy,projections regarding reliability of application and its components infield applications.

Generally two different types of mission profiles exist. Apre-determined mission profile refers to a mission profile that ispredetermined before the item is put in use and may be pre-programmed toa storage device, such as a non-volatile memory device. In contrast, a“smart” mission profile is an evolving mission profile that self-adjustsover time based on the output from on-board sensors, e.g., wear-outsensors, that sense the mission profile parameters under actualoperating conditions. Thus, a “smart” mission profile more closelyreflects the actual conditions that the component, the device or thesystem sees over its lifetime. The “smart” mission profile can beparticularly important in applications where specific mission profilesare not well known, because the “smart” mission profile can be updatedand improved periodically based on the changing output from the on-boardsensors. In the following, a mission profile monitoring systemcomprising on-chip wear-out sensors is described, according toembodiments.

Referring to FIG. 26, a block diagram of a mission profile monitoringsystem 260 comprising one or more wear-out sensors is illustrated formonitoring a mission profile of a component, a device or a system,according to embodiments. The component, a device or a system can beincluded or electrically connected to the core circuitry (not shown forclarity, see FIGS. 2A/2B). The one of more wear out sensors 2604 caninclude one or more of any of the wear-out sensors described herein,including sensors configured to measure wear-out from temperature,voltage, current, humidity, motion (e.g. vibration), etc. The system 260is configured to periodically generate measured output data 2608 fromthe wear-out sensors 2604 over the lifetime of the component, the deviceor the system. The output data can be stored in a first storage/memorycomponent 2612, which can be, e.g., a non-volatile memory device or avolatile memory device. The stored data can include instantaneous dataas well as statistical data, e.g., average data and variability data.The output data cumulated over time that is stored in the firststorage/memory component 2612 make up a “smart” mission profile 2616.

The system 260 additionally includes a predetermined mission profile2602, which includes a set of pre-determined mission profiles that canbe used as reference profiles. The predetermined mission profilesinclude temperature profile 2606, humidity profile 2610, bias (voltage)or current profile 2614, excitation profile 2618, vibration profile 2622and lifetime profile 2626, among other profiles. The predeterminedmission profile 2602 can be stored in a second storage/memory component2630, e.g., a non-volatile memory device or a volatile memory device.The system 260 additionally includes a modelling module 2634 that isconfigured to retrieve the predetermined mission profiles from thesecond storage component/memory component 2630 and to generate simulateddata 2616 of the wear-out state of the component, the device or thesystem using a predetermined set of physical models 2634.

The system 260 additionally includes a first comparator 2620 configuredto compare the simulated data from the modelling module 2634 and themeasurement output data from the on-chip wear-out sensors 2604. Theoutput from the first comparator 2620 can be sent to a signal processor2628 configured to determine the health of the component, the device orthe system being monitored based at least in part on the output from thefirst comparator 2620.

The system 260 may additionally include a second comparator 2624configured to compare the pre-determined mission profile 2602 and the“smart” mission profile 2616. The output from the second comparator canalso be sent to the signal processor 2628. The processor 2628 is furtherconfigured to, based on a deviation or a difference between thepre-determined mission profile and the “smart” mission profile,determine whether a system fault exists.

The monitoring system 260 can be used to monitor the mission profile ofthe component, the device or the system throughout its lifetime usingthe one or more wear-out sensors 2604. In some other embodiments, themonitoring system 260 can additionally employ an electrostatic discharge(ESD)/electrical overstress (EOS) monitor 2632. An output from theESD/EOS monitor 2632, which can signify a triggered event, can beutilized in conjunction with the output data from the one or morewear-out sensors 2604. When an ESD/EOS event occurs, the output from thewear-out sensors 2604 before and after the ESD/EOS event can becompared. Any significant change in output characteristics may indicatedamage internal to the IC that is induced by the ESD/EOS event. Suchinformation can also be stored in the first storage/memory component2612, e.g., non-volatile memory or a volatile memory, and cumulated overtime to make up the “smart” mission profile 2616.

In some embodiments, the system 260 additionally includes a device-levelreliability (DLR) modelling module, according to embodiments. The DLRmodelling module 2636 includes therein various modeling modules 2640associated with various wear-out mechanisms, including, e.g., hotcarrier injection (HCI) modelling module,time-dependent-dielectric-breakdown (TDDB) modelling module,electromigration (EM) modelling module, bias temperature instability(BTI) modelling module and magnetoresistance (MR) modelling module. Themodeling modules 2640 can also include one or more internet-of-things(IOT) sensor modelling modules including one or more of energyharvesting modelling module, gas-sensing modelling module, humiditysensing modelling module, resonator modelling module and biometricsensing modelling module, to name a few. Using these models and datafrom the “smart” mission profile, potential wear-out issues can bedetected and used to alert the user of latent system failure. The datacan also be used as part of a feedback loop 2644 to adjust theperformance of the component, the device or the system and/or toinitiate a redundancy protocol 2648. The system 260 additionally caninclude a communication module 2652, which include wired or wirelessmeans for alerting the user of potential or latent component, device orsystem failure. In some implementations, the data generated andtransmitted by the communication module 2652 can be encrypted forprotection.

Applications of mission profile monitoring include, e.g.:

-   -   Functional Safety Standard (FuSa ISO26262) applications;    -   Internet-of-Things (IOT) wear-out sensors;    -   Warranty Returns/Mis-use: The mission profile monitoring system        can be utilized to highlight component, device, or system        mis-use. For example, while the on-chip wear-out sensor can        monitor junction temperature it may be desirable to also monitor        the ambient temperature, which can help distinguish between an        IC fault, a product specific fault and a system fault. The        information stored on chip can be useful for failure analysis        and in particular warranty failures. The system can be utilized        in conjunction with an EOS/ESD monitor to aid fault analysis.    -   IC/System Redundancy Protocol: For safety critical applications,        redundancy is often desirable. The mission profile monitoring        system can be used to trigger the redundancy protocol prior to        IC/product failure hence preventing potential system damage via        thermal runaway and other effects.    -   Temperature Mapping: Some wear-out sensors capable of monitoring        temperature can be used in conjunction with the mission profile        monitoring system to map temperature gradients of systems. On        screen temperature maps can be displayed along with system        alerts to highlight wear-out and latent system failure.    -   Humidity Mapping: Some wear-out sensors capable of monitoring        humidity can be used in conjunction with the mission profile        monitoring system to map humidity gradients of systems. On        screen humidity maps can be displayed along with system alerts        to highlight wear-out and latent system failure.    -   Vibration Mapping: Some wear-out sensors capable of monitoring        vibration can be used in conjunction with the mission profile        monitoring system to map vibration gradients of systems. On        screen vibration maps can be displayed along with system alerts        to highlight wear-out and latent system failure.        Operating Voltage Guard Banding

FIGS. 27-28 illustrate a method of supply voltage guard-banding in ICdevices using wear-out monitor devices, according to embodiments. Whilenot shown, the sensing circuit 25 a/25 b described above with respect toFIGS. 2A/2B can be configured to implement the method described withrespect to FIGS. 27-28.

Generally, the operating voltage of an IC device can be determinedduring manufacturing test and characterization processes based on theIC's intended operating environment. Referring to FIG. 27, at the testand characterization steps, various extra margins can be added to theintrinsic minimum voltage, to arrive at an overall voltage guard bandingbudget 272. For example, a voltage droop guard band can be added to theguard banding budget 272 in an attempt to guarantee proper operationeven during worst-case voltage droop events, as illustrated in theschematic time evolution curve 270 of the guard-banded operating voltageof the IC device. Additional guard bands can be added, e.g., aging guardband.

Referring to FIG. 28, under typical conditions, the voltage droopexperienced by an IC device can be much smaller than under worst-caseconditions depicted in the time evolution curve 270, and the IC canoperate correctly with a much smaller guard band. However, because theactual wear-out state of the IC device that may be causing the voltagedroop is unknown, the IC devices are often operated under suchworst-case conditions. For example, referring to graph 280 of FIG. 28,the IC device may be operated under a “recommended Vdd” which mayrepresent the Vdd level which takes into account of the worst-caseconditions. However, using an unnecessarily large voltage guard band canwaste energy. By using various wear-out monitor devices, e.g., inconjunction with the lifetime indicator system 250 (FIG. 25) or missionprofile monitoring system 260 (FIG. 26), the amount of guard banding canbe minimized, thereby saving energy consumed by the IC device. That is,by tracking the actual wear-out state of the IC, the difference betweenthe recommended Vdd and the actual Vdd can be minimized, thereby savingvaluable energy.

Thus, in various embodiments, a method of voltage guard banding includesperiodically determining the wear-out state of the IC using a wear-outmonitor according to various embodiments described herein, anddetermining therefrom an instantaneous expected voltage droop thatcorresponds to the wear-out state. Once the expected instantaneousvoltage droop that corresponds to the wear-out state is determined, therecommended Vdd curve can be updated. By increasing the periodicity ofsuch determination, the amount of wasted energy can be minimized.

Self-Powering Wear-Out Monitors

FIG. 29 illustrates an IC apparatus 290 comprising a wear-out monitor291 and configured to wirelessly transmit the monitored data while usingminimum or no energy supplied by a power source, or using energyscavenged from the environment in the form of, e.g., solar energy,according to embodiments.

The IC apparatus 290 comprises a wear-out monitor 291, which can be oneof wear-out monitor devices described supra, a sensing circuit 294 forsensing the wear-out signal from the wear-out monitor device 291, awireless communications module 296 for wirelessly communicating thewear-out signal and an energy harvesting component 298 for powering thesensing circuit 295 and the wireless communications module 296. The ICapparatus 290 may also include a reference device 292, which can beconfigured as one of reference devices described supra. As describedsupra, the wear-out monitor device 291 and the reference device 292 relyon atomic diffusion and do not include a separate power supply tomonitor wear-out stresses that cause the atomic diffusion. However, thesensing circuitry 294 and the wireless communication module 296 canstill include a separate power supply. However, for usage in remote,harsh or otherwise difficult-to-access locations, e.g., top of askyscraper, a bridge or remote base stations, extended monitoring usingbattery power may not be desirable or practical. Advantageously, the ICapparatus 290 includes the energy harvesting component 298. Energyharvesting can involve converting a non-electrical form of energy intocharge. The energy harvesting component 298 can be any suitable deviceconfigured to harvest energy from the environment, e.g., a photovoltaicdevice, a thermoelectric device or a piezoelectric device. The energyharvesting component 298 is configured to partially or fully supply thepower to the sensing circuit 294 and the wireless communication module296 of the IC apparatus 290, such that the IC apparatus 290 can be usedfor an extended period of time in remote, harsh or otherwisedifficult-to-access locations, while receiving the monitor informationat the cost of little or no separate power supply. Furthermore, it willbe appreciated that the IC apparatus 290, by being remotely located fromprocessing circuitry (not shown for clarity) while being communicativelycoupled thereto using the wireless communication module 296, the monitordevice can be operated in an environment that is much more harsher thanthe environment in which the processing circuitry is operated, such as,e.g., a processing environment of a remote server.

Oxidation/Corrosion Wear-Out Monitors

In addition to detecting changes in the rate of atomic diffusion,chemical reactions, e.g., oxidation and/or corrosion reactions, can beused to gauge the wear-out level of some IC devices. Various reactionsbetween the environmental atoms and the monitor impurity atoms, whichcan include corrosion and/or oxidation, can provide a history of thewear-out stresses associated with the environmental atoms. According tovarious embodiments, substances/materials that chemically react, e.g.,corrode and/or oxidize, can additionally be included in monitor devicesthat include monitor impurity atoms, e.g., Au or other materials thatdiffuses at a defined/predictable rate. In some implementations, therate of reaction of oxidizing/corroding materials can be directlycorrelated to a measurable electrical quantity. In some otherimplementations, the oxidizing/corroding materials can produce adiscernible effect on the rate of diffusion of monitor impurity atoms,e.g., Au atoms, and thereby be indirectly correlated to a measurableelectrical quantity. A system can thus be constructed that could providean indication of a level of corrosion or oxidation, which could be usedindependently or in combination with other wear-out mechanisms andconditions described in other embodiments disclosed herein. Similar todiffusion, the wear-out stresses associated with oxidation and/orcorrosion can also be thermally activated, such that the conceptsdescribed above with respect to diffusion can be applicable in monitordevices described herein with respect to FIGS. 30A-30D.

FIGS. 30A-30D illustrate various embodiments of monitor devices 300a-300 d having structures that oxidize/corrode under various usageenvironments, where changes in the rate of oxidation/corrosion can beused to determine the state of wear-out of the core circuitry. Thestructures that oxidize/corrode can be used by themselves, i.e., withoutstructures that have monitor atoms configured to diffuse, or inconjunction with structures having monitor atoms configured to diffuse.When structures that oxidize/corrode are used in conjunction withstructures having monitor atoms that diffuse, the presence of structuresthat oxidize/corrode can affect the rate of diffusion of the monitoratoms, and the presence of structures having monitor atoms can affectthe rate of oxidation/corrosion. Such monitor devices can be configuredto detect wear-out stresses associated with certain environmental atoms,including various gases or liquids, e.g., oxygen, moisture, water, CO₂,etc.

Referring to FIGS. 30A-30D, each of the wear-out monitor devices 300a-300 d includes a substrate 302, which can include measurementstructures described supra, e.g., PN junctions or impedance measurementstructures, a diffusion barrier 304 formed thereon to limit or inhibitthe diffusion, oxidation, or corrosion of the underlying substrate 302.

Referring to FIG. 30A, the wear-out device 300 a includes a plurality oflayers 306 a of monitor atoms configured to diffuse into the underlyinglayers and a plurality of oxidizing layers 308 a that are adapted tooxidize at a predetermined rate for known oxidizing environments. Theoxidizing layers 308 a can include a metal or a semiconductor materialthat have known oxidation rates. The layers 306 a of monitor atoms andthe oxidizing layers 308 a laterally alternate in the illustratedembodiment.

Referring to FIG. 30B, the wear-out device 300 b is similarly arrangedas the wear-out device 300 a of FIG. 30A, except, instead oxidizinglayers of the monitor device 300 a, the wear-out device 300 b includes aplurality of layers 308 b that are adapted to corrode at a predeterminedrate for known corroding environments. The corroding layers 308 b of caninclude a metal or a semiconductor material that have known corrosionrates. The layers 306 b of monitor atoms and the corroding layers 308 alaterally alternate in the illustrated embodiment.

Referring to FIG. 30C, the wear-out device 300 c is similarly arrangedas the wear-out monitor devices 300 a/300 b of FIG. 3A/FIG. 30B, except,the wear-out device 300 c of FIG. 30C has a stacked configuration inwhich the oxidizing layer/corroding layer 308 is formed on top of thelayer 306 c of monitor atoms.

Referring to FIG. 30D, the wear-out device 30 d is similarly arranged asthe wear-out devices 300 c of FIG. 30C, except, instead of a stackedconfiguration in which the oxidizing layer 308 c is formed on top of thelayer 306 c of monitor atoms, the wear-out device 300 d of FIG. 30D theoxidizing layer/corroding layer 308 d formed below the layer 306 d ofmonitor atoms.

Wear-Out Monitor Arrays

FIG. 31 illustrates a plurality of wear-out monitor devices that arelaterally arranged as an array 310 a (cross-sectional view)/310 b (planview) of wear-out monitor devices 318, according to embodiments. Thearray 310 a/310 b can be implemented as part of a system, such a systemin a chip (SoC) or a system in a package (SIP). The array 310 a/310 bcomprises the plurality of monitor devices 318 formed over a substrate312 and can include a diffusion barrier 314. The monitor devices 318 maybe the same type or different types, depending on the application. Forexample, for some applications, some of the monitor devices 318 may beconfigured to monitor thermal stresses, while other monitor devices 318may be configured to monitor voltage or current stress. When the monitordevices 318 are of the same type, they may be configured to monitorstresses over the same or different stress ranges. For example, some ofthe monitor devices 318 may be configured to monitor wear-out under afirst temperature range, while others of the monitor devices 318 may beconfigured to monitor wear-out under a second temperature range. In someimplementations, the monitor devices 318 may interconnected andcommunicatively coupled by electrical links or connections 316 that mayallow for sensing a plurality of monitor devices 318 in series or inparallel. In some implementations, the electrical links 316 may be fuselink or antifuse links that can be modified after fabrication to form aparticular pattern of active monitor devices 318 to target specificregions of the core IC device and/or particular ranges of stresses(e.g., temperature range).

FIGS. 32A and 32B illustrate a plurality monitor device/reference devicepairs 320 (FIG. 32A) that are laterally arranged as an array 328 (FIG.32B), according to embodiments. The array 328 may be configuredsimilarly to the array 310 a/310 b of FIG. 31, and the description ofsimilar aspects will be omitted. However, unlike the array 310 a/310 bof FIG. 31, each monitor device 322 of the array 328 is paired with areference device 324, whose arrangements and advantages for reasonsdescribed supra.

FIGS. 33A-33B illustrate a plurality of monitor devices that arelaterally arranged as an array 330 a (cross-sectional view)/330 b (planview) of monitor devices 338 formed over a substrate 332 and a diffusionbarrier 334, according to embodiments. Similar to the array of wear-outmonitor device described above with respect to FIG. 31, the array 330a/330 b includes monitor devices 338 that are interconnected andcommunicatively coupled by electrical links or connections 336. Theelectrical links or connections 336 are configured to be intentionallyexposed to conditions that may result in their corrosion and/oroxidation, and are formed of materials that can corrode/oxidize undersuch conditions. As a result, a system is created in which a discernibleelectrical change develops over time based on the corrosion/oxidation(and potentially the consumption of the links or connections 336themselves). The array 330 a/330 b of FIGS. 33A-33B may be configuredsimilarly to the array 310 a/310 b of FIG. 31, and the description ofsimilar aspects will be omitted. Unlike the array 310 a/310 b of FIG.31, however, at least some of the monitor devices 338 have formedthereon a passivation layer 337 a, which can be a polymeric passivationlayer or a dielectric passivation layer.

FIG. 33C illustrates another embodiment of an array 330 c of monitordevices 338 a in which, unlike the passivation layer 337 a of FIG. 33A,the passivation layer 337 c forms a blanket layer over a plurality ofmonitor devices 338 a, except where openings 333 are formed through theblanket passivation layer 337 c. In the illustrated embodiment, an arrayof monitor device/reference device pairs 331 a/331 b, which includesmonitor devices 338 a/338 b and reference devices 339 a/339 b, similarto the monitor device/reference device pairs 320 of FIG. 32A, isillustrated. In the plan view of a portion of an array 330 c, exposedpairs 331 a are directly exposed to the environment, while unexposedpairs 331 b remain covered by the passivation layer 337 c. Theillustrated array 330 c may be particularly beneficial in monitoringenvironments where at least some of the monitor devices 338 a andreference devices 339 a are exposed to oxidizing or corrodingenvironments as described supra, while others of the monitor devices 338b and reference devices 339 b and of electrical links 336 are preventedfrom being exposed to oxidizing and/or corroding environments topreserve the integrity of the electrical interconnections between themonitor devices 338 a/338 b and the reference devices 339 a/339 b.

System in a Package Wear-Out Monitor

FIG. 34 is a diagram of a system in a package (SIP), or a system withembedded components embedded, e.g., systems with components embeddedwithin a substrate(s). 340 that includes one or more wear-out monitordevices 348, according to embodiments. In the illustrated embodiment,the substrate 342 has formed thereon the wear-out monitor devices 348 inclose proximity to core circuit devices 346 to be monitored, therebyproviding a relatively accurate indications of the level of wear of thecore circuit devices 346. For example, the wear-out monitor devices 348can be disposed immediately adjacent to the core circuit devices 346.The die 342 and the other components can be encased within a singlepackage to form the system 340. The monitor devices 348 can be disposedat a suitably specific location that may be a particular area ofconcern, e.g., suitably adjacent a high power device or asensitive/critical processing device. The SIP 340 can include an overmold compound 344 that encapsulates the die 342 and other components.The SIP 340 can be configured such that signals can be communicatedexternally to and from the SIP 340 by the die 342 and/or the othercomponents, for example, wirelessly or by being provided to an outputcontact of the SIP 340.

Electrical Overstress (EOS) and Electrostatic Discharge (ESD) Wear-OutMonitors

Transient electrical events such as electrostatic discharge (ESD),electrical overstress (EOS) or electromagnetic compatibility (EMC)transients can cause wear-out of IC devices. As described hereintransient electrical events are electrical events having a time durationless than DC regime. Without being bound to any theory, it has beenpredicted that there are three regimes of device failure due totransient electrical events. In the adiabatic regime, the duration oftransient electrical events is of the order of <100 ns. Due to suchshort duration, there is little heat transfer and the time-to-failroughly shows a 1/t correlation. In the thermal diffusion regime, theduration of transient electrical events is of the order of about 100 nsto about 10 ms. In this regime, heat transfer duration is of the orderof heat transfer time and the time-to-fail roughly shows a 1/t^(1/2)correlation. In the DC/steady state regime, the duration of electricalevents is greater than about 0.1/10 ms. In this regime, the device is inthermal equilibrium and the time-to-fail roughly shows no correlationwith time. These regimes have been described in what is known asWunch-Bell curve.

Various protection devices for protection against various transientelectrical events can be incorporated into apparatuses as off-chipmodules or be integrated on-chip, e.g., as part of a multi-die packagewith built-in protection. Various protection devices include acombination of PN diodes, BJTs and field-effect transistors. Usingvarious configurations of wear-out monitor devices described above withrespect to these and other devices, some protection devices can be usedto monitor wear-out caused by transient electrical events. According tovarious embodiments herein, a wear-out monitor device can detect noncatastrophic electrical overstress (EOS) events. Such functionality canmonitor an IC with slightly lower breakdown than other circuits andprovide wear-out information about the IC device.

FIGS. 35A and 35B illustrate schematic diagrams of ESD detectioncircuits 350 a and 350 b, respectively, according to embodiments. Eachof the ESD detection circuits 350 a and 350 b includes a first ESDprotection device 352 and a second ESD protection device 354.

The first ESD protection device 352 can include, e.g., a diode having arelatively low breakdown voltage and a relatively small physical areaand the second ESD protection device 352 include, e.g., a diode having arelatively high breakdown voltage and a relatively large physical area.These ESD protection devices can include diodes, bipolar junctiontransistors and semiconductor-controlled rectifiers (SCRs). The firstESD protection device 352 can trigger at a lower voltage than the secondESD protection device 354. In an illustrative example, the firstprotection device 352 can trigger at, e.g., about 6.5 Volts and thesecond ESD protection device 354 can trigger at, e.g., about 7 Volts.The second ESD protection device 354 can handle more current than thefirst ESD protection device 352. In the illustrated embodiment of FIG.35A, a resistor 355 (FIG. 35A) or a fuse 367 (FIG. 35B) is in serieswith the first ESD protection device 352, for example, to preventthermal runaway and/or to provide a voltage for the detection circuit356.

With the first ESD protection device 352, ESD events below the thresholdfor triggering the second ESD protection device 354 can be detected andassociated data can be used to determine the wear-out of a component,device or a system. The ESD protection offered by the first ESDprotection device 354 may not be sufficient to protect an internalcircuit, but the ESD protection offered by the first ESD protectiondevice 352 can provide a way to monitor what is happening in the secondESD protection device 354 without including a resistance, which shoulddiminish the effectiveness of the second ESD protection device 3544, inseries with the second ESD protection device 354.

The ESD detection circuits 350 a and 350 b can detect an ESD event usingthe voltage across the resistor 355 (FIG. 35A). Alternatively, thedetection circuit 350 b can blow the fuse 357 when an ESD event isdetected. After a certain number of ESD events (e.g., 10 events) aredetected, an alarm signal can be provided. For instance, the alarmsignal can be toggled when all fuses can be blown and/or memory cellscan overflow. The alarm signal can provide an alert to warn that adevice has been aged by ESD events.

EOS detection circuitry can provide functional safety information at thedie level and/or at a system level. At the die level, recording andmonitoring EOS events can provide an indication of the functional safetyof the die. Such information can be reported external to the die. Analarm signal can be provided external to the die to provide a warningabout the functional safety of the die and/or to suggest that action betaken, such as replacement of the die. At the system level, detectingEOS events can provide information about functional safety at a systemlevel. Such information can be used for predictive maintenance, forexample.

Certain physical layouts of ESD protection devices can be implementedfor high performance. The physical layouts discussed below can beimplemented in connection with any of the EOS protection devicesdiscussed herein. Example physical layouts are illustrated in FIGS. 36Ato 36C.

FIG. 36A provides an example of a physical layout of an ESD protectiondevice 360. In FIG. 37A, the ESD protection device is an annularstructure in plan view. This can enable relatively high current handlingcapability. Anode 362 and cathode 364 of the ESD protection device 360can be provided around a bond pad 366. The weakest point of an ESDprotection device can be at the end of a finger, even with increasedspacings, resistances and/or curvature, as this is the location of thattypically has the highest electric field. An annular ESD siliconcontrolled rectifier (SCR) can be used for system level ESD protectionto mimic a circular device enclosing a bond pad. Such a SCR can includeany combination of features described in U.S. Pat. No. 6,236,087, theentire technical disclosure of which is hereby incorporated by referenceherein.

An annularly shaped ESD protection device in plan view can have arelatively large perimeter area and hence a relatively large crosssectional area through which the current can flow. As one example, theperimeter can be about 400 μm and the diode junction can be about 3 μmdeep, thus the cross section area can be about 1200 μm². Additionally,with the annular structure, metal can come out from a bond pad on foursides. This can combine to substantially minimize the resistance to anESD zap and hence the voltage experienced by sensitive circuitryinternal in the chip can be substantially minimized. Another approachthat may provide an even lower resistance path to an ESD zap is a purevertical diode where the conduction is vertically down through thesilicon. In such a diode, for a 100 μm by 100 μm pad, the cross sectionarea is 10,000 μm² and the metal resistance can also be relatively smallas there can be a thick low resistance metal paddle on one side and alow resistance bond wire in close proximity on the other side.

In some instances, an ideal ESD device can be circular, as substantiallythe same electric field can be present along the entire a junction insuch a structure. Circular ESD device layouts may not be area efficientand/or an inner anode can be smaller in junction area than an outercathode. Circular ESD device layouts can conduct larger currents thansome other common ESD layouts that consume approximately the same area.Circular ESD device layouts can conduct relatively large currents, suchas currents associated with EOS events. Accordingly, such ESD devicelayouts can be desirable in certain applications in which an ESD deviceis used to harvest energy associated with an EOS event.

FIG. 36B provides an example of a physical layout of an ESD device 361.The physical layout of the ESD device 361 is a relatively large circularshape in plan view. This can reduce the difference between junction areabetween the anode 362 and the cathode 364.

FIG. 36C provides an example of a physical layout of an ESD device 368.The ESD device 368 is implemented by a relatively dense array of smallercircular ESD devices 369. The smaller circular ESD devices 369 can bebutted against each other laterally and/or vertically. An array ofsmaller circular ESD devices 369 can be implemented in wearablecomputing devices such as smart watches, for example.

FIG. 37A is a schematic diagram of a vertically integrated system 370 athat includes one or more wear-out or corrosion monitor devices 371integrated with an ESD protection and/or energy harvesting circuitry ona single chip, according to embodiments. A combined ESD protection andstorage chip 372 with the one or more wear-out monitor device includes,in addition to circuitry capable of harnessing energy from ESD eventsand storage elements configured to store charge associated with the ESDevents, circuitry for sensing the wear out level of the system orcomponents of the system. The combined chip 372 can be stacked with anASIC 374. Combining the ESD protection devices and storage elements in asingle die can reduce height of the vertically integrated systemrelative to two separate die stacked in a pyramid configuration.Combining the ESD protection devices and storage elements in a singledie can reduce the length and/or resistance of a path from a surgeconduction point and storage elements relative to two separately stackeddie. The ASIC 374 can receive charge from storage elements of thecombined chip 372. Having the energy harvesting circuitry on a differentchip than the ASIC can allow EOS protection devices, such as ESDprotection devices, to be scaled up to store charge from larger EOSevents, such as larger ESD events. It will be appreciated that the oneor more wear-out or corrosion monitor devices 371 can be integratedwithin any SIP (System in package) or system independently to monitor ormeasure different stress conditions, e.g., temperature, voltage, etc.,as discussed elsewhere herein.

FIG. 37B is a cross-sectional view 370 b of a fully packaged verticallyintegrated system 370 a illustrated in FIG. 37A. The cross-sectionalview 370 a shows an opening (or an aperture, a conduit or a path) 375formed through a packaging material (or a barrier or an encapsulant) 378such that air or moisture can directly contact the wear-out or corrosionmonitor device 371. The combined chip 371 and the ASIC main die areelectrically connected to each other and externally through wire bonding376, or some other suitable electrical connection or a conductive path.

FIG. 37C is a cross-sectional view a fully packaged verticallyintegrated system 370 c similar to that of the system 370 a/b of FIGS.37A/37B, except the system 370 c additionally includes micro electromechanical sensor (MEMS) 373 electrically connected to the sensor die.In addition, unlike the system 370 a/b of FIGS. 37A/37B, the system 370c additionally includes a plurality of through-silicon vias (TSVs) 377electrically connecting a wear-out or corrosion monitor device 371 to anASIC 374 (or a processing die within a system) that is physicallyseparated from the MEMS 373 and/or the ASIC 374 by a cavity 379. Byseparating the monitor device 371 from the MEMS 373 and/or the ASIC 374,the circuitry of the monitor device 371 could be selectively exposed,e.g., through openings formed at the package/module/system level.Advantageously, by doing so, the monitor device 371 can be keptseparated from the ASIC 374, and can be configured to be exposed tohigher temperatures and/or harsher environments. In the illustratedembodiment, the cavity 379 is formed by etching a portion of thesubstrate of the monitor device 371 such that the cavity overlaps withthe MEMS 373. However, embodiments are not so limited and other suitableprocesses can be used to dispose the cavity 379 between the monitordevice 371.

The combined chip 372 and the ASIC main die are electrically connectedto each other and externally through wiring 376. The combined chip 372can be electrically connected by one or more through-silicon vias(TSV's) 377 as illustrated, or using wire bonding 376 as illustrated inFIG. 37B.

Diffusion-Enhancing Monitor Device Structures

For some applications, it may be desirable to monitor effects ofmechanical wear-out stress on core devices. In some applications, thecore device to be monitored may be a static device under stress, e.g., atransistor device under a stress from adjacent shallow trench isolationor a semiconductor device under a stress from a flexible substrate onwhich it is formed. In other applications, the core device to bemonitored may be may be a dynamic device, e.g., a micro electromechanical system (MEMS) device. For these applications, it can bedesirable to monitor wear-out stress arising from such mechanicalwear-out stress.

Under some circumstances, mechanical stress can cause changes indiffusion rate of dopant atoms. FIGS. 38A-38E illustrate variousembodiments of wear-out monitor devices that are formed in or on aflexible substrate such that wear-out stresses associated withmechanical deformation can be monitored, e.g., by utilizing mechanicalstress-enhanced diffusion of monitor atoms. Each of monitor devices 380a-380 e has a plurality of doped regions formed in a flexible substrate383. The plurality of doped regions may form an array. The flexiblesubstrate 382 can be formed of a flexible material, e.g., flexiblepolymeric materials, or a semiconductor/dielectric substrate that hasbeen substantially thinned, e.g. to less than about 500 μm such that thesemiconductor/dielectric substrate is flexible. The substrate 382 may bedoped, e.g., lightly doped, with a first dopant type, or be undoped. Themonitor device is configured such that a mechanical deformation causedby, e.g., bending or deflection, results in an electrical signaturesassociated with the wear-out stress such as fatigue. In someembodiments, the substrate 382 may include or at least be partiallyformed of materials such as piezoelectric materials to convert themechanical deformations into electrical signals.

FIGS. 38A and 38B illustrate a wear-monitor device 380 a/380 b before(FIG. 38A) and after (FIG. 38B) the substrate 382 has undergone bending,according to embodiments. The monitor devices 380 a and 380 b each has aplurality of doped regions 384 a and 384 b, which can be doped with asecond dopant type. When the substrate 382 is doped with a first dopanttype, a PN junction is formed, such that depletion regions 386 a and 386b are formed, which can be used for detecting diffused monitor atoms, asdescribed with respect to various embodiments described supra. Asdescribed above, the doped regions 384 a and 384 b may include monitoratoms that are adapted to diffuse into the underlying substrate, e.g.,into the depletion region. In some embodiments, the monitor atoms may beformed on the doped regions 384 a and 384 b, while in other embodimentsthe monitor atoms may be formed in addition to, or to at least partiallyreplace the dopants of the doped region that is doped with the seconddopant type. In operation, bending of the monitor device 380 a into abent monitor device 380 b as shown in FIG. 38B results in the dopedregions 384 b being placed under either a tensile strain as shown, orunder a compressive strain when bent in an opposite direction (notshown). The tensile or compressive strain may change the rate of thediffusion of monitor atoms into the underlying substrate material, whosechange can be detected using the sensing circuit, as described supra.

FIG. 38C illustrates another wear-monitor device 380 c that isconfigured for monitoring stresses associated with mechanicaldeformation, according to embodiments. Similar to the wear-out device380 a/380 b of FIGS. 38A/38B, the wear-out monitor device 380 c has aplurality of doped regions 384 c in a flexible substrate 382. However,unlike the wear-out monitor device 380 a/380 b, the doped regions 384 care merged to form a plurality of connected doped regions 384 c and acorresponding depletion region 386 c.

FIGS. 38D and 38E illustrates additional embodiments of wear-out monitordevice 380 d and 380 e that are configured for monitoring stressesassociated with mechanical deformations, according to embodiments.Similar to the wear-out device 380 a/380 b of FIGS. 38A/38B, thewear-out monitor devices 380 c and 380 d have a plurality of first dopedregions 384 d and 384 e, respectively, in a flexible substrate 382.However, unlike the wear-out monitor device 380 a/380 b, the wear-outmonitor devices 380 d and 380 e have a plurality of second doped regions386 d and 386 e in a flexible substrate 382. The second doped regions386 d and 386 e may be oppositely doped compared to the first dopedregions 384 e and 384 e and configured as a punch-through monitor, asdescribed supra with respect to FIGS. 11A and 11B. In some embodiments,as illustrated in FIG. 38D, laterally adjacent first doped regions 384 dand laterally adjacent second doped regions 386 d may have similar orvarying dopant concentrations while having similar depths such that thevertical separation distances d₁ between corresponding first and seconddoped regions 384 d and 386 e is relatively constant. In some otherembodiments, laterally adjacent first doped regions 384 e and laterallyadjacent second doped regions 386 e may have similar or varying dopantconcentrations and different depths such that the vertical separationdistances d₂ between corresponding first and second doped regions 384 eand 386 e are varying, as illustrated and in the wear-out monitor device380 e of FIG. 380E.

For some applications, it may be desirable to monitor wear-out effectsresulting from electric field enhancement of certain device structures.In some applications, the core device to be monitored may havestructural features that having relatively sharp features, such thatelectric field is enhanced compared to adjacent regions. Furthermore,such enhancement of electric field can lead to EOS/ESD events, which canin turn produce lattice defects in semiconductor materials, throughwhich the rate of atomic diffusion can be substantially enhanced. Thus,for various applications, it is be desirable to monitor wear-out stressarising from such field-enhancement effects.

FIG. 39A illustrates a wear-out monitor device 390 a having one or moreserrated structures 392 a that can serve as electrodes under an electricfield. In some embodiments, upper and lower serrated structures 392 aand 392 b, respectively, are formed of a first material, which can be asemiconductor material or a conductive material. The serrated structures392 a/392 b are interposed by an interposed structure 394 formed of asecond material, which can be a semiconductor material or a dielectricmaterial. In the illustrated embodiment, the first material comprises asemiconductor material doped with a first dopant type, e.g., n-type, andthe second material comprises a semiconductor material dope with asecond dopant type, e.g., p-type. The wear-out monitor device 390 a ofFIG. 39A includes monitor atoms, which can be present in either of theserrated structure 392 a or the interposed structure 394, where themonitor atoms are configured to diffuse in the wear-out monitor device390 a. The serrated structures 392 a/392 b comprise a plurality offield-enhancement regions 396 that are configured to enhance electricfield when an electric field is applied between the upper and lowerserrated structures 392 a/392 b. In the illustrated embodiment, a gap d₁and/or radii of curvature between different pairs of opposingfield-enhancement regions 396 can vary, such that different pairs can besubject to a discharge event, e.g., EOS/ESD events, under differentelectric field values. When one or more EOS/ESD events occur betweenpairs of opposing field-enhancement regions 396, certain lattice defects398, e.g., stacking faults or dislocations, can form, thereby providingan enhanced diffusion paths for monitor atoms. In operation, by applyingan electric field between the upper and lower serrated structures 392 a,an EOS/ESD event can be induced therebetween, leading to enhanced atomicdiffusion of monitor atoms, e.g., through lattice defects 398 in theserrated structures 392 a/392 b. A level of wear-out of a monitoredstructure, e.g., in the core circuit, can be determined therefrom, asdescribed above.

In some embodiments, a reference device 390 b illustrated in FIG. 39Bcan be provided with the wear-out monitor device 390 a of FIG. 39A.Unlike the monitor device 390 a, the reference device 390 b comprisesupper and lower regions 393 a and 393 b, respectively, formed of thesame material as the serrated structures 392 a/392 b of the monitordevice 390 a (FIG. 39A), and an interposed structure 395 formed of thesame material as the interposed structure 394 of the monitor device 390a (FIG. 39A). In operation, by applying a similar electric field betweenthe upper and lower structures 393 a and 393 b as the electric fieldapplied between upper and lower serrated structures 392 a and 392 b, anEOS/ESD event can be induced between upper and lower serrated structures392 a and 392 b, while a similar EOS/ESD event is not induced betweenupper and lower structures 393 a and 393 b. Therefore, the level ofwear-out of a monitored structure, e.g., in the core circuit, can bedetermined, as described above.

FIG. 40 is an illustration of a wear-out monitor device 400 comprisingmonitor atoms that are configured to diffuse in a semiconductor materialand configured such that a stress condition causes a change in the rateat which the monitor atoms diffuse in the semiconductor substrate 450,according to embodiments. The wear-out monitor device includes,laterally on one or both sides, isolation regions 401 a, e.g., shallowtrench isolation regions. The wear-out monitor device additionallyincludes a buried layer 401 b, which may be a buried oxide layer 401 b,such as a buried oxide (BOX) of a silicon-on-insulator (SOI). Thus, thedevice 400 may be electrically isolated from surrounding regions by theisolation regions 401 a and the buried layer 401 b. In some embodiments,the semiconductor substrate 450 may at least an upper portion in whichvarious doped regions are formed, which may be an epitaxial region. Theillustrated wear-out monitor device 400 additionally comprises a buriedlayer region 462 vertically above the buried oxide layer 401 b andlaterally extending between the isolation regions 401 a. The wear-outmonitor device 400 additionally includes a first doped region 458 formedwithin the semiconductor substrate 450 and may or may not be in contactwith the buried layer region 462. The substrate 450, the buried layerregion 462 and the first doped region may be doped with the same dopanttype, according to some embodiments. For example, the substrate 450 maydoped with a first dopant type, which may be an n-type dopant or ap-type dopant, at a first concentration. The first doped region 458 maybe doped with the first dopant type at a higher concentration relativeto the substrate 450. Similarly, the buried layer region 458 may bedoped with the first dopant type at a higher concentration relative tothe substrate 450. In the illustrated embodiment, each of the substrate450, the first doped region 458 and the buried layer region 462 aredoped with an n-type dopant.

The wear-out monitor device 400 includes a first heavily doped region454 a doped with the first dopant type. In the illustrated embodiment ofFIG. 40, the first doped region 454 a is a heavily doped n-doped (n+)region. The wear-out monitor device 400 additionally includes a seconddoped region 454 b that is doped with a second dopant type opposite tothe first dopant type. In the illustrated embodiment, the second dopedregion 454 b is an p-doped region, e.g. a heavily doped (p+) region.

In the illustrated embodiment, a portion of the substrate 450 forms anintervening region which laterally separates the first and second dopedregions 454 a and 454 b such that is doped either with the first orsecond dopant types, at a concentration substantially lower than thefirst or second heavily doped regions 454 a or 454 b. In the illustratedembodiment, the intervening region is an n-doped region. Thus, thewear-out monitor device 400 can include first and second heavily dopedregions 454 a and 454 b and the first doped region 458 and the substrate450 intervening the first and second doped regions 454 a and 454 b suchthat a PN junction comprising, e.g., p+ second heavily doped region 454b/the substrate 450/the first doped region 458/n+ first heavily dopedregion 454 a formed of P+/N−/N/N+ regions, in one example embodiment.However, it will be appreciated that various doped regions of thewear-out monitor device 400 are illustrated by way of example only, andother embodiments are possible, where each of the p+ second heavilydoped region 454 b, the substrate 450, the first doped region 458 and n+first heavily doped region 454 a is doped to form any one of P⁺, P, P⁻,N⁺, N or N⁻ regions, such that a PN junction is formed.

In the wear-out monitor device 400 of FIG. 40, the first and seconddoped regions 454 a and 454 b are formed by implanting respectivedopants through openings formed in the dielectric layer 463; however,embodiments are not so limited. For example, other masking (e.g.,photoresist) and doping (e.g., diffusion) techniques may be used in lieuor in addition to using the dielectric layer 463 as an implantationmask.

Still referring to FIG. 40, the wear-out monitor device 400 additionallyincludes a first electrode 408 a and a second electrode 408 b formedover the first heavily doped region 454 a and over the second heavilydoped region 454 b, respectively, through openings in dielectric layer463. One or both of the first and second electrodes 408 a and 408 bcomprise or is formed of the monitor atoms, and serves as a reservoir ofthe monitor atoms, as described supra. In the illustrated embodiment,the first electrode 408 a and a second electrode 408 b are formed onfirst adhesion layer 412 a and a second adhesion layer 412 b,respectively. As described supra with respect to FIGS. 6A/6B, theadhesion layers 412 a, 412 b can enhance adhesion of the first andsecond electrodes 408 a, 408 b. One or both of the first and secondelectrodes 408 a and 408 b are configured such that, when the wear-outmonitor device is subjected to a set of predetermined conditions for apredetermined duration, some of the monitor atoms in the respectiveelectrodes diffuse thorough the respective first and second heavilydoped regions 454 a and 454 b into a depletion formed thereunder.Depending on the concentration and/or depth of the diffused monitoratoms in the underlying semiconductor material, e.g., in the depletionregion, a cumulative wear-out history, e.g., a cumulative thermalwear-out history, of the monitor device 400 can be at least indirectlydetermined.

Thus, as configured, the wear-out monitor device 400 has one or morereservoirs of monitor atoms (i.e., first and/or second electrodes 408 a,408 b) disposed on a surface of the substrate and a monitor region(e.g., depletion region formed underneath the second heavily dopedregion 454 b) formed in the substrate 450. The monitor atoms havediffusion characteristics in the semiconductor material of the substratesuch that when the wear-out monitor device is subjected to a set ofpredetermined stress conditions for a predetermined duration, some ofthe monitor atoms diffuse into the monitor region. The reservoir caninclude, e.g., an electrode containing the monitor atoms or a layerformed of the monitor atoms. The monitor region can include a region inthe substrate, e.g., a depletion region formed by a PN junction asdescribed above, for example.

Various embodiments of the wear-out monitor device including thewear-out monitor device 400 of FIG. 40 are configured such that anelectrical property, or an electrical signature, associated with thepresence of the monitor atoms in the monitor region can be measured. Theelectrical signature can be, for example, any one or more of: junctionleakage, junction capacitance, junction built-in potential, junctionreverse recovery time, bipolar base transit time (fT),metal-oxide-semiconductor (MOS) transistor threshold voltage, MOStransistor subthreshold swing, MOS channel leakage, punch-throughbreakdown voltage (BV) and impact ionization breakdown voltage (BV), toname a few.

FIG. 41A illustrates a graph 410A showing experimental current-voltage(IV) curves 412 under reverse bias and breakdown under reverse bias offabricated wear-out monitor devices similar to the device schematicallyillustrated in FIG. 40. The IV curves 412 are those of 50 differentas-fabricated devices, indicating a high degree of device-to-deviceuniformity in electrical performance, as indicated by similar breakdownvoltages (BV) and leakage currents between different devices.

FIG. 41B illustrates a graph 410B showing experimental current-voltage(IV) curves under reverse bias of a fabricated wear-out monitor devicesimilar to the device schematically illustrated in FIG. 40, after beingsubject to different durations of thermal stress at 200° C. Inparticular, the IV curves 416 a-416 e represent measurements taken aftervarious bake times, including as fabricated (416 e), after baking forapproximately 1 day (416 d), after baking for approximately 2 days (416c), after baking for approximately 3 days (416 b) and after baking forapproximately 4 days (416 a), As illustrated, the leakage currentincreases with increasing bake time.

FIG. 41C illustrates a graph 410C showing experimental current-voltagecurves under forward bias of a fabricated wear-out monitor devicesimilar to the device schematically illustrated in FIG. 40. Inparticular, the IV curves 418 represent overlapping measurements under aforward bias, taken after various bake times, including as-fabricatedand after baking for approximately 1 day to 4 days, corresponding to IVcurves (416 e-416 a) of FIG. 41B under reverse bias.

FIG. 42A illustrates a chart 420A plotting experimentally measuredleakage currents under reverse bias of a fabricated wear-out monitordevice similar to the device schematically illustrated in FIG. 40, afterbeing subjected to different durations of thermal stress at 200° C. Thechart 420A shows a plot 422 of experimental leakage current measured at5 V after being subject to different durations of thermal stress at 200°C. In particular, the plot 422 plots measurements taken after variousbake times, including as fabricated and after baking for approximately1-9 days. As illustrated, the leakage current increases with increasingbake time.

FIG. 42B is a chart 420B plotting calculated leakage currents under areverse bias after being subjected to different durations of thermalstress at different temperatures, based on the chart 420A of FIG. 42Awhich plots experimentally measured leakage currents of a fabricatedwear-out monitor device similar to the device schematically illustratedin FIG. 40. In particular, the chart 420B shows calculated plots 424,426 and 428, whose calculations are based on the experimental leakagecurrents illustrated above with respect to the plot 422 of FIG. 42A,which represents measurements taken after various bake times, includingas fabricated and after baking for approximately 1-9 days. For example,without being bound to any theory, the leakage current density as afunction of bake time can be calculated based on an expression that canbe derived analogously to a time-dependent diffusion equation based onFick's Second Law, for example. Based on such expression, experimentallydetermined time dependence of leakage current at one bake temperaturecan be used to predict the time dependence of leakage current at otherbake temperatures. As illustrated, the leakage current increases at afaster rate with increasing bake temperature.

FIG. 42C is a contour chart 420C plotting leakage currents under areverse bias after being subjected to different durations of thermalstress at different temperatures, based on the chart 420A of FIG. 42A,which plots experimentally measured leakage currents, and based on thechart 420B of FIG. 42B, which plots calculated leakage currents, of afabricated wear-out monitor device similar to the device schematicallyillustrated in FIG. 40. Based on such a contour plot, a predictive timeand temperature dependence of leakage current can be determined for anytemperature range and any time range in which the diffusion of monitoratoms is expected to follow a predictive behavior, as discussed supra.

Wear-Out Monitor Devices Configured with Controlled Activation

As described above, the wear-out monitor devices according to variousembodiments have monitor atoms whose rate of diffusion changes inresponse to stress conditions. As described above, wear-out monitordevices based on atomic diffusion have many advantages, including theability to monitor wear out of a core circuit regardless of whether thecore circuit and/or the wear-out monitor device is activated, becauseatomic diffusion can occur independent of whether the core circuitand/or the wear-out monitor device is activated. However, for someapplications, it may be desirable to control the timing of a startingpoint of monitoring. In the following, embodiments of wear-out monitordevices are described, in which the starting point or the time ofinitiation of the diffusion the wear-out monitor device can becontrolled by, e.g., preventing or limiting the atomic diffusion untilthe wear-out device is initialized or activated by using, e.g., avoltage pulse or a current pulse to a diffusion region having thediffusant. Various embodiments disclosed below address these and otherneeds.

FIG. 43A illustrates a wear-out monitor device 430 configured to recordan indication of wear out of a core circuit based on atomic diffusion ofmonitor atoms that is localized within the wear-out monitor device,according to embodiments. FIG. 43B illustrates a close-up view of themonitor device 430 of FIG. 43A. In particular, the wear-out monitordevice 430A/430B comprises a first region, e.g., a reservoir 434comprising the monitor atoms that is separated from a second region,e.g., a substrate 62, by a barrier 438. The wear-out monitor device isconfigured such that the monitor atoms diffuse through the barrier andinto to the second region in response to an electrical stimulus. Themonitor device has monitor atoms having a diffusion activation energy inthe substrate that is between about 0.5 eV and about 3.5 eV, accordingto embodiments. Similar to the monitor device 60 described above withrespect to FIGS. 6A and 6B, the wear-out monitor device 430 comprises asemiconductor substrate 62 and monitor atoms configured to diffusetherein, wherein the monitor atoms are configured such that a stresscondition causes a change in the rate at which the monitor atoms diffusein the semiconductor substrate 62. Various regions of the monitor device

The wear-out monitor device 430 includes a first doped region 64 dopedwith a first dopant type, which can be n-type or p-type. In theillustrated embodiment, the first doped region 64 is a heavily dopedp-doped region, e.g., a heavily doped (p⁺) region.

The wear-out monitor device 430 additionally includes a second dopedregion 66 that is doped with a second dopant type opposite to the firstdopant type, i.e., p-doped when the first doped region 64 is n-doped,and vice versa. In the illustrated embodiment, the second doped region66 is an n-doped region, e.g. a heavily doped (n+) region.

The wear-out monitor device 430 additionally includes the reservoir 434of the monitor atoms. In some embodiments, the reservoir 434 serves as afirst electrode 68 a contacting the first doped region 64, in a similarmanner as described above with respect to FIGS. 6A/6B. In theseembodiments, the wear-out monitor device 430 additionally includes asecond electrode 68 b (not shown) contacting and the second doped region66. In some other embodiments, the reservoir 434 does not serve as anelectrode. In these embodiments, the monitor device 430 further includesa first electrode 68 a contacting the first doped region 64 and a secondelectrode 68 b contacting the second doped region 66, where thereservoir 434 containing the monitor atoms may be disposed between thefirst and second electrodes 68 a and 68 b. A detailed description ofvarious other structural features of the wear-out monitor device 430that are similar to corresponding features of the wear-out monitordevice 60 of FIG. 6A/6B, is omitted herein.

The reservoir 434 can be formed of various materials that incorporatethe monitor atoms. For example, when configured as the first electrode68 a, the reservoir 434 can be similar to the first electrode 68 adescribed above with respect to FIGS. 6A/6B, e.g., with respect to anelectrically conducting composition that comprises or is formed of themonitor atoms and serves as a reservoir of the monitor atoms. However,in embodiments where the reservoir 434 does not or need not serve as anelectrode, the composition of the reservoir 434 need not be electricallyconducting. For example, the monitor atoms can be formed of or includean electrically insulating material which contains, is impregnated with,is doped or otherwise is saturated with the monitor atoms such thatwhile serving as a reservoir, the reservoir 434 itself need not beelectrically conducting. For example, the reservoir 434 can be formed ofor include a dielectric material (e.g., oxides, nitrides, polymers,etc.) or be formed of or include a semiconductor doped with a relativelylow concentration of electrically active dopants.

As a further difference from wear-our monitor devices illustrated above,the reservoir 434 may be separated from the semiconductor substrate 62by the barrier 438. In the illustrated embodiment, the barrier 438 isinterposed between the reservoir 434 and the substrate 62 and enclosesthe reservoir 434. As formed, the barrier 438 is a physical barrierformed of a material that blocks diffusion of the monitor atoms from thereservoir 434 to the substrate 62 without being altered.

FIGS. 44A and 44B illustrate three- and two-dimensional energy-spacediagrams 440A and 440B depicting potential barriers as “seen” by amonitor atom in a wear-out monitor device such as that illustrated abovewith respect to FIGS. 43A/43B, according to embodiments. The well regionof the diagram 440A and the left region of the diagram 440B represent,in energy space, the energy level as “seen” by the monitor atom in thereservoir 434, and the outside-the-well region of the diagram 440A andthe right region of the diagram 440B represent, in energy space, theenergy level as “seen” by the monitor atom in the substrate 62. Asillustrated, the reservoir 434 and the substrate 62 are separated by aphysical barrier having an energy level as “seen” by the monitor atomsthat is higher than the energy levels of the reservoir 434 and thesubstrate 62. The height of the energy barrier is such that, underordinary operating conditions of the core circuit, e.g., within thermalenergy corresponding to temperatures less than or equal to about 85° C.,125° C. or 250° C., for example, the probability of atoms overcoming theenergy barrier is negligible. That is, the difference in average energylevels, ΔE, between the barrier 438 and the reservoir 434 may be, e.g.,substantially higher than (kT˜0.023 eV), e.g., 0.058 eV (400° C.) orhigher, 0.75 eV (600° C.) or higher, 0.092 eV (800° C.) or higher, 0.11eV (1000° C.) or higher, according to embodiments. Thus, at temperatureslower than the ΔE between the barrier 438 and the reservoir 434, therate of diffusion of the monitor atoms through the barrier 438 that isassociated with thermal energy of the monitor atoms (e.g., kT) may benegligible. Thus, without altering the barrier 438, the monitor atomsare substantially prevented from diffusing into the substrate 62.

In the embodiment illustrated with respect to the energy-space diagram440B, the energy levels of the reservoir 434 and the substrate 62 aresubstantially similar. Such may be the case, e.g., when the reservoir434 may be formed of the same material as the substrate, e.g., silicon,and impregnated with the monitor atoms, e.g., gold. However, embodimentsare not to limited, and the energy levels of the reservoir 434 and thesubstrate 62 may be substantially different. Such may be the case, e.g.,when the reservoir 434 may be formed of a different material than thesubstrate, e.g., an electrode metal impregnated with the monitor atoms,e.g., gold.

In some embodiments, the ΔE between the barrier 438 and the reservoir434 may correspond to, e.g., the difference in activation energies ofthe monitor atoms in the barrier 438 and the reservoir 434. In theseembodiments, the activation energy of the monitor atoms in the barrier438 may be greater than the activation energy of the monitor atoms inthe reservoir 434 by, e.g., 0.058 eV (400° C.) or higher, 0.75 eV (600°C.) or higher, 0.092 eV (800° C.) or higher, 0.11 eV (1000° C.) orhigher, according to embodiments.

Examples of insulating or dielectric materials used for the barrier 438include various inorganic dielectric materials compatible withsemiconductor processing, e.g., SiO_(x), SiO_(x)N_(y), and SiN_(x), toname a few. Examples of insulating or dielectric materials used for thebarrier 438 also include various inorganic or organic polymericmaterials compatible with semiconductor processing, includingelectroactive polymers and conjugated conducting polymers. For example,the barrier 438 can be formed of polypyrrole (PPy), poly3,4-ethylenedioxythiophene (PEDOT),poly[2-methoxy-5-(2′-ethylhexyloxy)-p-phenylene vinylene] (MEH-PPV),polyfluorene, fluorocarbon films, polytetrafluoroethylene (PTFE), amongvarious other suitable polymeric materials, where the monitor atoms“see” the higher barrier as described above, according to embodiments.Advantageously, these materials can be formed using various depositionprocesses that are compatible with semiconductor processing, e.g.,chemical vapor deposition, atomic vapor deposition, or physical vapordeposition, among other processes.

Examples conductive materials used for the barrier 438 include variousmetals or doped semiconductors compatible with semiconductor processing,in which the monitor atoms “see” the higher barrier as described above,according to embodiments.

According to embodiments, the barrier 438 is formed of an insulating ora conductive material configured such that, in response to an electricalstimulus, e.g., a voltage or a current stimulus, the barrier 438 issubstantially altered, or lowered. Alternatively or additionally, inresponse to an electrical stimulus, e.g., a voltage or a currentstimulus, the diffusant or the monitor atoms gain sufficient energy todiffuse into a substrate. In various embodiments, the alteration of thebarrier 438 or the gaining of sufficient energy by the diffusantinitiates or activates the wear-out monitor device 430, such that themonitor atoms begin to diffuse into the substrate under various stressessubjecting the core circuit, as described supra.

In some embodiments, the voltage or the current stimulus may in turninduce Joule heating of a monitor region below the reservoir 434. In theillustrated embodiment, the Joule heating may occur in a manner similarto Joule heating of a current monitor described above with respect toFIG. 8. Except for the reservoir 434 being disposed between the firstelectrode 68 a and the second electrode 68 b, the configuration of thewear-out monitor device 430 may be structurally similar to the wear-outmonitor device 80 described above with respect to FIG. 8. In addition toor in lieu using the current between the first and second electrodes 68a, 68 b to measure the effect of diffusion rate of the monitor atomscaused by Joule-heating, the current flowing between the first andsecond electrodes 68 a, 68 b is used to alter the barrier 438 thermallyand/or electrically. To alter the barrier 438 by Joule heating ofwithout substantially diffusing the monitor atoms into the substrate,the monitor region below the reservoir 434, represented as a resistorformed in series with the forward-biased PN junction between the firstelectrode 68 a and the second electrode 68 b in FIGS. 43A/43B, may besubjected to a transient voltage or a current pulse. The voltage orcurrent pulse may be applied under a bias condition in which the PNjunction of the wear-out monitor device 430 is forward-biased, such thatsufficient current density may be supplied for efficient Joule heating.In response to the forward bias, the series resistor of the monitorstructure generates sufficient heat, which causes the barrier 438 to bealtered, e.g., permanently altered, such that the ΔE is substantiallylowered or eliminated. For example, under the Joule heating, the barrier438 may develop structural modifications, e.g., bond breakages orpinholes. Once the ΔE is substantially lowered or eliminated, the atomicdiffusion of monitor atoms occur as in various embodiments describedabove. For example, once the barrier 438 is altered by a voltage or acurrent pulse, when the wear-out monitor device 430 is subsequentlysubjected to a set of predetermined conditions for a predeterminedduration, some of the monitor atoms in reservoir 434 diffuse into adepletion region formed between the first and second doped regions 64,66. Depending on the concentration and/or depth of the diffused monitoratoms in the underlying semiconductor material, e.g., in the depletionregion, a cumulative wear-out history, e.g., a cumulative thermalwear-out history, of the device 60 can be at least indirectlydetermined. Further details of the device structure and the operation ofthe monitor device 430 that have been described above will be omitted.Thus, as described above, the wear-out monitor device 430 depicted bythe energy-space diagrams 440B can be configured as, e.g., ause-activated wear-out monitor.

FIG. 45 illustrates a two-dimensional energy-space diagram 450 depictingpotential barriers as “seen” by a monitor atom in a wear-out monitordevice, according to embodiments. In particular, the energy-spacediagram 450 corresponds to a wear-out monitor device similar to thewear-out monitor device 430 except, the barrier 438 is omitted. Inaddition, unlike the wear-out monitor described with respect to theenergy-space diagram 440B (FIG. 44B), in which the energy levels of thereservoir 434 and the substrate 62 are substantially similar, thewear-out monitor device corresponding to the energy-space diagram 450the energy levels of the reservoir 434 (left side) is substantiallylower than the energy level of the substrate 62 (right side). Such maybe the case, e.g., when the reservoir 434 is be formed of a differentmaterial than the substrate, e.g., an electrode metal impregnated withthe monitor atoms or an electrode formed of the monitor atoms, e.g.,gold. In these embodiments, while the barrier 438 is omitted, themonitor atoms still “see” a barrier represented by the difference ΔE₂ inthe energy levels between the reservoir 434 and the substrate 62. TheΔE₂ may be similar, greater or smaller in magnitude compared to the ΔEdescribed above with respect to FIG. 44. Thus, while, unlike the monitordevice 430 described above with respect to FIG. 43, the barrier 438 isomitted, the monitor atoms nevertheless overcomes a barrier prior todiffusing into the substrate 62. The barrier ΔE₂ can be overcome by themonitor atoms upon receiving an electrical energy, e.g., a current or avoltage pulse, which results in the Joule heating of the monitor regionbelow the reservoir 434, in a similar manner as described above withrespect to FIG. 43. The monitor atoms that have overcome the energybarrier ΔE₂ can now diffuse further into the substrate 62, in a mannersubstantially similar to various embodiments described above.

FIG. 46 illustrates a two-dimensional energy-space diagram 460 depictingpotential barriers as “seen” by a monitor atom in a wear-out monitordevice, according to embodiments. In particular, the wear-out monitordevice depicted by the energy-space diagram 460 is similar to thewear-out monitor device described above with respect to the energy-spacediagram 450 (FIG. 45), except, the depicted wear-out monitor deviceadditionally includes, similar to the wear-out monitor device depictedabove with respect FIG. 43, a barrier 438. Similar to the energy-spacediagram 450, the energy levels of the reservoir 434 (left side) is lowerthan the energy level of the substrate 62 (right side), and the barrier438 is formed within the reservoir 434. Such may be the case, e.g., whenthe reservoir 434 is be formed of a different material than thesubstrate, e.g., an electrode metal impregnated with the monitor atomsor an electrode formed of the monitor atoms, e.g., gold, and the barrier438 is formed within the reservoir 434. As a result, the reservoir 434is divided by the barrier 438 into a first (left) region and a second(right) region. In these embodiments, when the barrier 438 is lowered oreliminated by, e.g., Joule heating via an electrical pulse, the wear-outmonitor device is initialized, in a similar manner as described abovewith respect to FIGS. 43 and 44A/44B. However, the monitor atoms still“see” a barrier represented by the difference ΔE₂ in the energy levelsbetween the reservoir 434 and the substrate 62. Thus, in addition to andsubsequent to being initialized by lowering or removing the barrier 438in a similar manner as described above with respect to FIGS. 43 and44A/44B, the monitor atoms additionally overcomes the second barrier ΔE₂prior to diffusing further into the substrate 62 in a similar manner asdescribed above with respect to FIG. 45.

FIG. 47 is an illustration of a wear-out monitor device 470 configuredto record an indication of wear out of a core circuit based on atomicdiffusion of monitor atoms that is localized within the wear-out monitordevice, according to embodiments. In particular, the monitor device 470includes monitor atoms arranged in accordance with the energy-spacediagram depicted in FIG. 45, where the energy level of the monitor atomsin the reservoir is substantially lower than the energy level of themonitor atoms in the substrate. Various structures of the monitor device470 are arranged similarly to those of the monitor device describedabove with respect to FIG. 40. For instance, the monitor device 470 islaterally isolated by isolation regions 401 a, e.g., shallow trenchisolation regions, formed on one or both sides, and a buried layer 401b, which may be a buried oxide (BOX) layer 401 b extending laterallybelow the active regions of the wear-out monitor device 470. Thewear-out monitor device 470 additionally comprises a buried layer (NBLY)region 462 vertically above the buried oxide layer 401 b and laterallyextending between the isolation regions 401 a. The wear-out monitordevice 400 additionally includes a first doped region 458 formed withinthe semiconductor substrate 450. The substrate 450, the buried layerregion 462 and the first doped region may be doped with the same dopanttype, according to some embodiments. For example, the substrate 450 maydoped with a first dopant type, which may be an n-type dopant or ap-type dopant, at a first concentration. The first doped region 458 maybe doped with the first dopant type at a higher concentration relativeto the substrate 450. Similarly, the buried layer region 458 may bedoped with the first dopant type at a higher concentration relative tothe substrate 450. In the illustrated embodiment, each of the substrate450, the first doped region 458 and the buried layer region 462 aredoped with an n-type dopant. The wear-out monitor device 400 includes afirst heavily doped region 454 a, e.g., a heavily doped n-doped (n+)region and a second heavily doped region 454 b, e.g., a heavily dopedp-doped (p+) region. Detailed relative doping concentrations andprocessing methods of various doped regions may be similar to asdescribed above with respect to FIG. 40, and their detailed descriptionswill be omitted.

Still referring to FIG. 47, the wear-out monitor device 470 additionallyincludes a first electrode 408 a and a second electrode 408 b formedover the first heavily doped region 454 a and over the second heavilydoped region 454 b, respectively, through openings in dielectric layer463. One or both of the first and second electrodes 408 a and 408 bserve as a reservoir of monitor atoms similar to the reservoir 434illustrated above with respect to FIG. 43, which comprise or is formedof the monitor atoms that are arranged in accordance with theenergy-space diagram depicted in FIG. 45. That is, one or both of thefirst and second electrodes 408 a and 408 b have monitor atoms arearranged such that the energy level of the monitor atoms in thereservoir is substantially lower than the energy level of the monitoratoms in the substrate.

Thus, as configured, the wear-out monitor device 470 has one or morereservoirs of monitor atoms (i.e., first and/or second electrodes 408 a,408 b) disposed on a surface of the substrate and a monitor region(e.g., depletion region formed underneath the second heavily dopedregion 454 b) formed in the substrate 450. The relative energy levels ofthe monitor atoms in the reservoir and the substrate are such that, uponovercoming the energy barrier ΔE₂ as described above with respect toFIG. 45, the monitor atoms in the semiconductor material of thesubstrate further diffuse into the monitor region of the substrate asdescribed above with respect to FIG. 40. That is, when the wear-outmonitor device is subjected to a set of predetermined stress conditionsfor a predetermined duration, some of the monitor atoms diffuse into themonitor region, where the monitor region can include a region in thesubstrate, e.g., a depletion region formed by a PN junction as describedabove, for example. Various electrical properties of the monitor regionthat can be measured has been described above with respect to FIG. 40,and is omitted herein.

FIG. 48 is an illustration of a wear-out monitor device 480 configuredto record an indication of wear out of a core circuit based on atomicdiffusion of monitor atoms that is localized within the wear-out monitordevice, according to some other embodiments. In particular, the monitordevice 480 includes monitor atoms arranged in accordance with theenergy-space diagram depicted in FIG. 44A/44B or 46, where a barrier 438is present between the reservoir and the substrate that has an energybarrier that is higher than the energy levels of the reservoir and thesubstrate. The energy level of the monitor atoms in the reservoir may besubstantially similar (FIG. 44A. 44B) or substantially lower (FIG. 46)compared to the energy level of the monitor atoms in the substrate.Various structures of the monitor device 480 are arranged similarly tothose of the wear-out monitor device 470 described above with respect toFIG. 47, except for the presence of the barrier 438, whose descriptionsare omitted herein. In addition, various physical properties as well asphysical and energy configurations of the barrier 438 have beendescribed above with respect to FIGS. 43, 44A/44B and 46, and areomitted herein.

FIGS. 49A-49F illustrate electrical responses of a wear-out monitordevice 490 configured to record an indication of wear out of a corecircuit based on atomic diffusion of monitor atoms that is localizedwithin the wear-out monitor device, according to some other embodiments.FIG. 49A illustrates a cross-sectional view of the structures of themonitor device 490, which includes monitor atoms arranged in a similarmanner as in the wear-out monitor device 470 illustrated above withrespect to FIG. 47, where the energy level of the monitor atoms in aplurality of reservoirs 438 is substantially lower than the energy levelof the monitor atoms in the substrate, such that the wear-out monitor490 is activated upon application of an electrical pulse to the aplurality of reservoirs 438. The arrangements of various structures ofthe monitor device 490 are substantially similar to the wear-out monitordevice 470 illustrated above with respect to FIG. 47 except that thewear-out monitor device 490 includes a plurality of reservoirsconfigured as first electrodes 408 a. FIG. 49B illustrates an exampleelectrical pulse 492 that can be applied to the reservoirs 438. In theillustrated embodiment, the reservoirs 438 configured as the firstelectrodes 408 a are in contact with a p-doped region, e.g., a heavilydoped p+ region formed within an n-doped region, e.g., an n-dopedepitaxial region, and the electrical pulse applied is a positive voltageapplied between the first electrodes 408 a and the second electrodes 408b, such that the PN junction formed by the p-doped region and then-doped region is forward-biased. FIG. 49C illustrates a cross-sectionalview of the simulated current density distribution 490 c resulting fromthe electrical pulse illustrated in FIG. 49B; FIG. 49D illustrates across-sectional view of the simulated heat distribution 490 d resultingfrom the Joule heating; FIG. 49E illustrates a cross-sectional view ofthe simulated impact ionization distribution 490 e resulting from theelectrical pulse illustrated in FIG. 49B; and FIG. 49F illustrates across-sectional view of the simulated potential gradient distribution490 f resulting from the electrical pulse illustrated in FIG. 49B. Forthe various simulations illustrated with respect to FIGS. 49C-49F, thePN junction formed by the heavily doped p+ region formed within then-doped region in the wear-out monitor device 490 of FIG. 49A isconfigured such that, under a voltage pulse illustrated with respect toFIG. 49B having a nominal pulse width of about 100 ns at a nominalvoltage of about 20V between the first electrodes 408 a and the secondelectrodes 408 b, the PN junction is forward biased and the peak currentdensity exceeding about 1×10³ A/cm² is achieved, as illustrated in FIG.49B, which in turn induces a peak temperature exceeding about 420K (orabout 147° C.), as illustrated in FIG. 49D.

In the above with respect to FIGS. 43-49, various embodiments ofwear-out monitor devices having a monitor structure are described, wherethe monitor structure is configured to be initialized prior to servingas a wear-out monitor based on atomic diffusion. For variousapplications, it may be desirable for a wear-out monitor device toinclude a plurality of monitor structures, where each monitor devicesincludes a reservoir and can also include a barrier, as described below.

FIG. 50A illustrates a cross-sectional view of a wear-out monitor device500 configured to record an indication of wear out of a core circuitbased on atomic diffusion of monitor atoms that is localized within thewear-out monitor device, where the wear-out monitor device 500 includesa plurality of monitor structures D1, D2, . . . Dn. Each one of themonitor structures D1, D2, . . . Dn includes a reservoir 434 accordingto any of the embodiments described above with respect to FIGS. 43-49,and can also include a barrier 438 according to any of the embodimentsdescribed above with respect to FIGS. 43, 44A/44B, 46 and 48. In theillustrated embodiment, each of the monitor structures D1, D2, . . . Dnhas nominally the same structures and are separated by nominally thesame spacing. Such configuration may be advantageous, e.g., forobtaining a spatial profile of wear-out stresses, obtaining atime-evolution of wear-out stresses and/or for initializing differentregions of the wear-out monitor device at different times and/orconditions, as described further infra, among other advantages. However,embodiments are not so limited, as illustrated in FIG. 51.

FIG. 50B illustrates an example implementation of a control circuithaving a current supply transistor 504 electrically connected to thewear-out monitor device and configured to supply the electricalstimulus. In particular, the current supply transistor is a sufficientlylarge transistor such that, as illustrated above with respect to FIGS.49C and 49D, a peak current density exceeding about 1×10³ A/cm², about1×10⁴ A/cm² or about 1×10⁵ A/cm² can achieved, according to embodimentsas illustrated in FIG. 49B, which in turn can induces a peak temperatureof about 420K (or about 147° C.), 470K (or about 197° C.) or about 520K(or about 247° C.).

FIG. 51A illustrates a cross-sectional view (upper drawing) and atop-down plan-view (lower drawing) of a wear-out monitor device 510Aconfigured to record an indication of wear out of a core circuit basedon atomic diffusion of monitor atoms that is localized within thewear-out monitor device. In the illustrated embodiment, the wear-outmonitor device 510A includes a plurality of different monitor structuresG, F, D, and E. Similar to the wear-out monitor device 500 illustratedabove with respect to FIG. 50, each one of the monitor structures G, F,D, E includes a reservoir 434 according to any of the embodimentsdescribed above with respect to FIGS. 43-49, and can also include abarrier 438 according to any of the embodiments described above withrespect to FIGS. 43, 44A/44B, 46 and 48. However, unlike the wear-outmonitor device 500, in the illustrated embodiment, each one of themonitor structures G, F, D, E is configured differently compared to anadjacent one of the monitor structures, with respect to one or more ofthe structures including the reservoir and/or the barrier, includingtheir material compositions, dimensions and or lateral configurations.In addition to obtaining a spatial profile of wear-out stresses, forobtaining a time-evolution of wear-out stresses, and/or for initializingdifferent regions of the wear-out monitor device at different timesand/or conditions, the configuration of the wear-out monitor device 510Amay further be advantageous for obtaining different rates of diffusionin different regions, among other advantages.

FIG. 51B illustrates a cross-sectional view of a wear-out monitor device510B configured to record an indication of wear out of a core circuitbased on atomic diffusion of monitor atoms that is localized within thewear-out monitor device, according to some other embodiments. Thewear-out monitor device 510B includes a plurality of different monitorstructures D1, D2 . . . Dn each having a differently arranged barrier.In particular, the different monitor structures D1, D2 . . . Dn can havethe barriers having thicknesses H1, H2, . . . Hn, respectively, suchthat the different monitor structures are initialized under differentelectrical stimuli, e.g., different voltage pulses. In addition, thedifferent monitor structures D1, D2 . . . Dn can include differentmonitor atoms and/or different matrix material including the monitoratoms when the reservoir is formed of a matrix containing the monitoratoms.

FIG. 52 illustrates a top-down plan-view of a wear-out monitor device520 configured to record an indication of wear out of a core circuitbased on atomic diffusion of monitor atoms that is localized within thewear-out monitor device, where the wear-out monitor device 520 includesan array having a plurality of rows, e.g., a first row R1 includingmonitor structures D1, D2, . . . Dn and a second row R2 includingmonitor structures D4, D5, . . . Dm. The array can further have aplurality of columns, e.g., a first column C1 including monitorstructures D1, D4, . . . Di and a second column C2 including monitorstructures D2, D5, . . . Dj. The monitor structures D1, D2, . . . Dn andD4, D5, . . . Dm can be nominally the same, as described above withrespect to FIG. 51, or be nominally different, as described above withrespect to FIG. 52. In the illustrated embodiment, the monitorstructures are configured to be electrically connected in a regulararray having a plurality of rows R1, R2, . . . and/or columns C1, C2, .. . . In some embodiments, the electrical connections can be such thateach of the rows including the monitor structures D1, D2, . . . Dn canbe electrically accessed, e.g., for initialization, in parallel and/orsimultaneously. In some other embodiments, the electrical connectionscan be such that each of the discrete monitor structures can beelectrically accessed individually, e.g., for initialization, in a“bit-addressable” manner by applying appropriate electrical signals to aparticular rows and a column. The array configuration of may beadvantageous, e.g., for obtaining a spatial profile of wear-outstresses, for obtaining a temporal and/or spatial evolution of wear-outstresses and/or for initializing different regions of the wear-outmonitor device at different times and/or conditions, as describedfurther infra, among other advantages.

FIG. 53 illustrates a top-down plan-view of a wear-out monitor device530 configured to record an indication of wear out of a core circuitbased on atomic diffusion of monitor atoms that is localized within thewear-out monitor device, where the wear-out monitor device 530 includesan array having a plurality of monitor structures D1, D2, . . . Dnarranged at different radial distances from a reference point or acentral position, according to embodiments. Similar to the wear-outmonitor device 520 illustrated above with respect to FIG. 52, themonitor structures D1, D2, . . . Dn can be nominally the same, asdescribed above with respect to FIG. 51, or be nominally different, asdescribed above with respect to FIG. 52. Unlike FIG. 52, however,instead of being arranged to have rows and/or columns, the monitorstructures D1, D2, . . . Dn of the wear-out monitor device 530 arearranged such that the monitor structures have different radialdistances r1, r2, . . . rn, respectively, relative to a central positionor a central structure H, which may be a heat source. The arrayconfiguration of may be advantageous, e.g., for obtaining a spatialprofile of wear-out stresses, e.g., a radial profile, for obtaining atemporal and/or spatial evolution of wear-out stresses and/or forinitializing different regions of the wear-out monitor device atdifferent times and/or conditions, as described further infra, amongother advantages.

In the above with respect to FIGS. 43-53, various embodiments ofwear-out monitor devices having a monitor structure are described, wherethe monitor structure is configured to be initialized prior to servingas a wear-out monitor based on atomic diffusion in a vertical direction,e.g., in a direction normal to the substrate surface, and into thesubstrate. For various applications, it may be desirable for a wear-outmonitor to include a monitor structure that is configured to beinitialized prior to serving as a wear-out monitor based on atomicdiffusion in a lateral direction, e.g., in a direction parallel to thesubstrate surface.

FIGS. 54A and 54B illustrate a cross-sectional view and a top downplan-view of a wear-out monitor device 540 configured to record anindication of wear out of a core circuit based on atomic diffusion ofmonitor atoms that is localized within the wear-out monitor device,according to embodiments. The wear-out monitor 540 is configured to beinitialized prior to serving as a wear-out monitor based on atomicdiffusion in a lateral direction, according to embodiments. Unlike themonitor device illustrated above with respect to, e.g., FIG. 43, in themonitor device 540, the monitor atoms have a net direction of diffusionthat is a lateral direction along a substrate surface. Referring toFIGS. 54A and 54B, the illustrated wear-out monitor device 540 includesa substrate 62 having formed thereon a monitor region 544, e.g., acircular monitor region, surrounded by a recessed region 546, e.g., acircular recessed region. The wear-out monitor device 540 additionallyincludes, formed in the recessed region 546, a reservoir 434surrounding, e.g., circularly surrounding, the monitor region 544, and abarrier 438 surrounding, e.g., circularly surrounding, the reservoir434. The monitor region 544 can have a lateral dimension, e.g., adiameter, E adapted such that the monitor atoms diffusing laterally cangive an indication of a wear-out of the core circuit during its lifetime. The recessed regions 546 have a depth F adapted for accommodatingthe reservoir 434 and the barrier 438. Except for the lateralarrangement, various other configurations including materials, energeticrelationships between the monitor region 544, the barrier 438 and thereservoir 434, the possibility of omission of the barrier 438, andvarious semiconductor doped regions that the monitor region 544 caninclude, are substantially similar to various embodiments describedabove, and as such, their detailed descriptions are omitted herein.

In some embodiments, the monitor region 544, the reservoir 433 and thebarrier 438 can be separated from the bulk substrate by a permanentdiffusion barrier 548. While the illustrated embodiment includes themonitor region 544, the barrier 438 and the reservoir 434 configured ascircularly concentric regions. However, other embodiments are possible,where the monitor region 544, the barrier 438 and the reservoir 434 areconfigured as any suitable shape adapted for recording an indication ofwear out of a core circuit based on atomic diffusion of monitor atoms ina lateral direction, according to embodiments.

FIGS. 55A-55C illustrate top down plan-views of wear-out monitor devices550A, 550B and 550C, respectively, that are configured to record anindication of wear out of a core circuit based on atomic diffusion ofmonitor atoms that is localized within the wear-out monitor device,according to embodiments. Similar to the wear-out monitor device 540illustrated with respect to FIGS. 54A/54B, the wear-out monitor devices550A, 550B and 550C are configured to be initialized prior to serving asa wear-out monitor based on atomic diffusion in a lateral direction,according to embodiments. However, unlike the monitor device illustratedabove with respect to FIGS. 54A/54B, in which the monitor atoms diffusein a radially inward direction, e.g., inward from the reservoir towardsthe monitor region formed at a central location, in the wear-out monitordevices 550A, 550B and 550C, the monitor atoms diffuse in a radiallyoutward direction, e.g., outward from the reservoir formed at a centrallocation towards the monitor region formed at an outer location. Each ofthe wear-out monitor devices 550A, 550B and 550C includes a substrate 62having formed thereon one or more monitor structures 550-1, 550-2,550-3, . . . 550-n. While four monitor structures are illustrated, therecan be one or any suitable number of monitor structures that can beincluded in a manner similar to the illustrated four monitor structures.

Each of the one or more monitor structures 550-1, 550-2, 550-3, . . .550-n include a dedicated or shared reservoir having, e.g., a circularshape, a dedicated or shared barrier having, e.g., a circular or a ringshape, surrounding the dedicated or shared reservoir, and a respectiveone of monitor regions 552-1, 552-2, 552-3, . . . 552-n extending in aradial direction. Each of the one or more monitor regions 552-1, 552-2,552-3, . . . 552-n has one end contacting the barrier 438 such thatmonitor atoms crossing the barrier 438 can diffuse in a radial directionalong one of the monitor regions 552-1, 552-2, 552-3, . . . 552-n. Inthe illustrated embodiment, each one or more monitor regions 552-1,552-2, 552-3, . . . 552-n is formed as a strip, a track or a channelstructure extending in a lateral direction parallel to the substratesurface such that monitor atoms diffuse laterally outward in each of theone or more monitor regions 552-1, 552-2, 552-3, . . . 552-n.

According to embodiments, the one or more monitor regions 552-1, 552-2,552-3, . . . 552-n can be formed of the same or different materials, canhave the same or different dimensions (e.g., lengths) or can otherwisehave the same or different configurations, such that different ones ofthe one or more monitor regions 552-1, 552-2, 552-3, . . . 552-n candiffuse the monitor atoms at different rates and/or differentconcentration profiles.

Still referring to FIGS. 55A-55C, each of the monitor regions 552-1,552-2, 552-3, . . . 552-n has a length and one or more measurementstructures 554 formed along the length for measuring an electricalproperty associated with each of the monitor regions. For the example,the one or more measurement structures 554 can include, e.g., contactsor probes, for measuring the electrical property associated with each ofthe monitor regions. In some embodiments, neighboring ones of the moremeasurement structures 554 may be separated by a constant distance.

In some embodiments, the reservoir 434, the barrier 438 and the one ormore monitor regions 552-1, 552-2, 552-3, . . . 552-4 may be formed onthe substrate 62, e.g., a common planar substrate.

In some other embodiments, at least the reservoir 434 and the barrier438 may be formed in a recessed region formed in the substrate 62. Therecessed region may, e.g., be an inverse of the recessed regiondescribed above with respect to FIGS. 54A/54B. For example, the barrier438 may be formed by depositing the barrier material on sidewalls of arecessed region formed at a central location, e.g., on sidewalls of acircular recessed region, and depositing the reservoir material in therecessed region, e.g., in the circular recessed region,

In addition, the one or more monitor regions 552-1, 552-2, 552-3, . . .552-n may be formed in the substrate 62, e.g., when the one or moremonitor regions 552-1, 552-2, 552-3, . . . 552-n are formed of amaterial different from the substrate. For example, the one or moremonitor regions 552-1, 552-2, 552-3, . . . 552-n formed by first formingrecessed regions having the shape of the one or more monitor regions552-1, 552-2, 552-3, . . . 552-n and filling the recessed regions withthe material of the one or more monitor regions 552-1, 552-2, 552-3, . .. 552-4.

Each of the one or more monitor regions 552-1, 552-2, 552-3, . . . 552-nhas a lateral dimension, e.g., a length adapted such that the monitoratoms diffusing radially outward can give an indication of a wear-out ofthe core circuit during its life time. The reservoir 434 and the barrier438 can have thicknesses corresponding to the depth F adapted foraccommodating the reservoir 434 and/or the barrier 438 in a recessedregion, as described above with respect to FIGS. 54A/54B. Except for thelateral arrangement, various other configurations including materials,relative energy levels between the monitor region 544, the barrier 438and the reservoir 434, the possibility of omission of the barrier 438,and various semiconductor doped regions that the monitor region 544 caninclude, are substantially similar to various embodiments describedabove, and as such, their detailed descriptions are omitted herein.

In operation, upon lowering or eliminating the energy barrier associatedwith the barrier 438 by an electrical stimulus the wear-out monitordevice is initialized, as described supra. After being initialized, inresponse to a wear-out stress, the monitor atoms start to diffuse fromthe reservoir 434 into the one or more monitor regions 552-1, 552-2,552-3, . . . 552-n that are elongated in a lateral direction. Theplurality of measurement structures 554 located at intervals along thelength direction of each of the one or more monitor regions 552-1,552-2, 552-3, . . . 552-n can provide a spatially-dependent electricalindication, e.g., leakage current. The spatially-dependent electricalindication can in turn provide a temporal history of the wear-stressexperienced by the core circuit, based on the time-dependence of thediffusion of monitor atoms described supra.

Referring to the monitor device 550A of FIG. 55A, in some embodiments,the one or more monitor regions 552-1, 552-2, 552-3, . . . 552-n contacta common barrier 438 and are configured to be supplied with monitoratoms from a common reservoir 434. As configured, the plurality ofmeasurement structures 554 located at intervals along the lengthdirection of each of the one or more monitor regions 552-1, 552-2,552-3, . . . 552-n can provide spatially-dependent electrical indicationin different directions, which can in turn provide a correspondingtemporal history of the wear-stress experienced by the core circuit.

Referring to the monitor device 550B of FIG. 55B, in some embodiments, aseparate barrier 438-B1, 438-B2, 438-B3 and 438-B4 is dedicated for eachof the one or more one or more monitor regions 552-1, 552-2, 552-3, . .. 552-n are the same. The barriers 438-B1, 438-B2, 438-B3, . . . 438-Bncan be physically separated by a thermally robust division that does notbecome substantially altered in response to an electrical stimulus thatalters the barriers 438-B1, 438-B2, 438-B3, . . . 438-Bn. Each of theseparate barriers 438-B1, 438-B2, 438-B3, . . . 438-Bn is configured tobe independently modified by an electrical stimulus, such that the eachof the one or more monitor regions 552-1, 552-2, 552-3, . . . 552-n isconfigured to initialized independently from each other. Thus, aplurality of wear-out indications can be initialized at different timesbased on a user's preference.

In some embodiments, the separate barriers 438-B1, 438-B2, 438-B3 . . .438-Bn can be formed of same or different materials, have the same ordifferent dimensions (e.g., thicknesses) or otherwise have the same ordifferent configurations such that they are configured to be alteredcorrespondingly in response to the same or different electrical stimuli.

Referring FIG. 55C, in some embodiments, in addition to separatebarriers 438-B1, 438-B2, 438-B3, . . . 438-B4 for the one or moremonitor regions 552-1, 552-2, 552-3, . . . 552-n as described above withrespect to FIG. 55B, the monitor device 550C can additionally includeseparate reservoirs 434-A1, 434-A2, 434-A3, . . . 434-An dedicated foreach of the one or more monitor regions 552-1, 552-2, 552-3, . . .552-n. The barriers 438-B1, 438-B2, 438-B3, . . . 438-Bn can beconfigured as described above with respect to FIG. 55B. In addition,each of the separate reservoirs 434-A1, 434-A2, 434-A3, . . . 434-A4 canbe configured to independently supply the monitor atoms to be diffusedin the one or more monitor regions 552-1, 552-2, 552-3, . . . 552-n,after a corresponding one of the barriers 438-B1, 438-B2, 438-B3, . . .438-Bn is modified by an electrical stimulus, such that the each of theone or more monitor regions 552-1, 552-2, 552-3, . . . 552-n isconfigured to initialized independently from each other and to beindependently supplied with the monitor atoms. Thus, in addition tobeing initialized at different times based on user's preference. aplurality of wear-out indications can be independently supplied with themonitor atoms.

In some embodiments, the separate reservoirs 434-A1, 434-A2 434-A3, . .. 434-An can contain the same or different monitor atoms, can containthe same or different matrix material incorporating the monitor atoms,have the same or different dimensions (e.g., volumes) or otherwise havethe same or different configurations, such that they are configured tosupply the same or different monitor atoms to the respective ones of theone or more monitor regions 552-1, 552-2, 552-3, . . . 552-n.

Thus, in the illustrated embodiment in FIG. 55C, different ones of theone or more monitor structures 550-1, 550-2, 550-3, . . . 550-n havingdifferent combinations of the reservoir, the barrier and the monitorregion can be configured to be particularly sensitive to differenttypes, different magnitudes and/or different durations of wear-outstresses. For example, each of the one or more monitor structures 550-1,550-2, 550-3, . . . 550-n can be adapted for different temperatureranges and/or different durations of wear-out stresses.

In the embodiments described above with respect to FIGS. 55A-55C,various embodiments of a wear-out monitor device including a pluralityof monitor structures configured to be initialized prior to serving as awear-out monitor based on atomic diffusion in a lateral direction aredescribed. In particular, in the embodiments described above withrespect to FIGS. 55A-55C, the plurality of monitor structures arearranged laterally on a substrate. In the following, embodiments of awear-out monitor device including a plurality of monitor structures thatare arranged vertically, e.g., in a vertically stacked configuration,are described. The monitor structures according to these embodiments canoccupy a more compact lateral footprint and provide indications ofwear-out stress at different depths within the monitor device. Similarto the embodiments described above with respect to FIGS. 55A-55C, theseembodiments can have the same or different barriers, the same ordifferent reservoirs of monitor atoms, and/or the same or differentmonitor regions.

FIG. 56A illustrates a cross-sectional view of a wear-out monitor device560A that is configured to record an indication of wear out of a corecircuit based on atomic diffusion of monitor atoms that is localizedwithin the wear-out monitor device, according to embodiments. Similar tothe wear-out monitor devices 550A, 550B and 550C described above withrespect to FIGS. 55A-55C, the wear-out monitor 560A is configured to beinitialized prior to serving as a wear-out monitor based on atomicdiffusion in a lateral direction, according to embodiments. However,unlike the monitor devices illustrated above with respect to FIGS.55A-55C, in which the monitor structures are arranged laterally on asubstrate, the monitor structures of the monitor device 560A includes aplurality of monitor structures 562-1, 562-2, . . . 562-n formed on asubstrate 62 including corresponding ones of monitor regions 564-1,564-2, . . . 564-n. The monitor regions 564-1, 564-2, . . . 564-n areseparated from a reservoir 464 by a barrier 468. Each of the pluralityof monitor regions 562-1, 562-2, . . . 562 n are elongated and extend ina radial direction and has one end contacting the barrier 438 such thatmonitor atoms crossing the barrier 438 can diffuse away from thereservoir 434 in a radial direction along a length direction.Furthermore, the substrate 64 is separated from the reservoir 434 suchthat it can also serve as a monitor region. In the illustratedembodiment, each one or more monitor regions 564-1, 564-2, . . . 564-nis formed as a strip, a track or a channel structure extending in alateral direction parallel to the substrate surface such that monitoratoms diffuse laterally outward in each of the one or more monitorregions 562-1, 562-2, . . . 562-n.

Still referring to FIG. 56A, similar to embodiments illustrated withrespect to FIGS. 55A-55C, in some embodiments, the monitor device 560Ahas the monitor regions 562-1, 562-2, . . . 562-n that are formed of thesame or different materials, have the same or different dimensions(e.g., lengths) or otherwise have the same or different configurations,such that different ones of the monitor regions 562-1, 562-2, . . .562-n are configured to diffuse the monitor atoms at different ratesand/or different concentration profiles. However, embodiments are not solimited and in other embodiments, the monitor regions 562-1, 562-2, . .. 562-n are configured to be substantially the same.

FIG. 56B illustrates a cross-sectional view of a wear-out monitor device560B similar to the wear-out monitor device 560A of FIG. 56A, includingelectrical connections to the reservoir 434 and to the monitor regions562-1, 562-2, . . . 562-n. As illustrated, the wear-out monitor device560A includes a plurality of electrical contacts 566-1, 566-2, . . .566-n, e.g., via contacts, electrically connecting the monitor regions562-1, 562-2, . . . 562-n to various circuitry, including, e.g., controlcircuitry and/or sensing circuitry, as described more in detail, infra.In addition, a plurality of electrical contacts 566-(n+1), 566-(n+2), .. . 566-(n+m), e.g., via contacts, electrically connecting the reservoir434 and the substrate 64 to various circuitry, including, e.g., controlcircuitry and/or sensing circuitry, as described more in detail, infra.

Referring to an equivalent circuit diagram 560C of FIG. 56C, each of theregions of the monitor regions 562-1, 562-2, . . . 562-n of the wear-outmonitor device 560 is initialized by individually applying an electricalstimulus to a respective region of the barrier 438 between the reservoir434 and the each of the monitor regions 562-1, 562-2, . . . 562-n viarespective ones of the electrical connections, thereby locally alteringthe respective region of the barrier 438. Once initialized, the monitoratoms start to diffuse from the reservoir 434 into the respective one ofthe monitor regions 562-1, 562-2, . . . 562-n in response to a wear-outstress. Thus, as configured, by altering respective regions of thebarrier 438 at different times, different ones of the monitor regions562-1, 562-2, . . . 562-n can advantageously be initialized at differenttimes according to the user's preference. In embodiments where themonitor regions 562-1, 562-2, . . . 562-n are formed of the samematerial and/or otherwise configured to have the substantially the samerate of diffusion of the monitor atoms therein, a plurality ofmonitoring runs can be performed using the plurality of the monitorregions 562-1, 562-2, . . . 562-n. Furthermore, by configuring themonitor regions 562-1, 562-2, . . . 562-n to have different lengths asillustrated in FIG. 56A, different monitoring runs can be performed fordifferent durations of time. In addition, where the monitor regions562-1, 562-2, . . . 562-n are formed of different materials and/orotherwise configured to have the substantially different rates ofdiffusion of the monitor atoms therein, different ones of the monitorregions 562-1, 562-2, . . . 562-n optimized for different wear-outstresses or levels of the wear-out stress can be initialized atdifferent times according to a user's preference. For example, where acore circuit is experiences substantially different levels of thermalwear-out stresses at different times, a barrier region adjacent to oneof the monitor regions 562-1, 562-2, . . . 562-n configured to diffusethe monitor atoms relatively slowly and/or having a longer monitorregion length may be altered when the core circuit is exposed to arelatively high level of thermal stress (e.g., relatively highertemperature and/or relatively long duration). On the other hand, abarrier region adjacent to one of the monitor regions 562-1, 562-2, . .. 562-n configured to diffuse the monitor atoms relatively rapidlyand/or having a shorter length may be altered when the core circuit isexposed to a relatively lower level of thermal stress (e.g., relativelylower temperature and/or relatively shorter duration). By way ofexample, different ones of the monitor regions 562-1, 562-2, . . . 562-nmay be formed of or include a material AxBy having differentcompositions, where A and B are elements that can be proportionallymixed to alter the diffusion rate of monitor atoms therein. For example,A may be a substrate material such as Si, and B may be Ge, C, Sn, O, andN, to name a few.

After being initialized and being subjected to wear-out stresses,changes in the electrical properties of monitor regions 562-1, 562-2, .. . 562-n resulting from diffusion of monitor atoms from the reservoir434 into the monitor regions 562-1, 562-2, . . . 562-n can be measuredthrough the plurality of electrical contacts 566-1, 566-2, . . . 566-n,e.g., using a suitable sensing circuitry. FIG. 56D illustrates oneexample embodiment of a wear-out monitor device 560D having a sensingcircuit 568 electrically connected to the wear-out monitor device 560Bof FIG. 56B and configured to measure the changes in electricalproperties of the monitor regions 562-1, 562-2, . . . 562-n. In theillustrated example, the monitor regions 562-1, 562-2, . . . 562-n areelectrically connected to a differential measurement circuit 568including a differential amplifier and configured to, based on adifference in the measured electrical properties of from different onesof the monitor regions 562-1, 562-2, . . . 562-n, a determination ofrelative wear-out stress received by the different monitor regions562-1, 562-2, . . . 562-n can be determined. The differentialmeasurement circuit 568 can measure difference(s) in the electricalproperties between any two or more of the monitor regions 562-1, 562-2,. . . 562-n, which can arise from varying any one of the monitor atoms,the reservoir composition, the composition of the monitor regions 562-1,562-2, . . . 562-n, the shapes and dimensions of the monitor regions562-1, 562-2, . . . 562-n, barrier material and initialization times,among other parameters arising from various configurations of thewear-out device 560 described above. The resulting electricalmeasurement can include any one of electrical properties describedabove, e.g., resistivity, leakage current, capacitance, etc.

Referring to FIG. 56E, a cross-sectional view of a wear-out monitordevice 560E is illustrated, according to some other embodiments. Thewear-out monitor device 560D is similar to the wear-out monitor device560A/560B described above with respect to FIGS. 56A/56B, except, thewear-out monitor device 560D has two sets 568-1, 568-2 of monitorregions commonly connected to a reservoir. The monitor regions on thetwo sides can be configured to be the same or different, including thebarrier and the monitor regions.

While in the illustrated embodiment of FIGS. 56A/56B, the one of themonitor regions 562-1, 562-2, . . . 562-n are connected to a commonreservoir 434 through a common barrier 438, embodiments are not solimited. For example, while not shown, in other embodiments, separateand/or dedicated barriers 438-B1, 438-B2, . . . 438-Bn and/or separateand/or dedicated reservoirs 434-A1, 434-A2, . . . 434-An may beconnected to respective ones of the monitor regions 562-1, 562-2, . . .562-n. Thus, in a similar manner as described above with respect to theembodiment of FIG. 55C, in addition to being configurable to have thesame or different monitor regions 562-1, 562-2, . . . 562-n, the monitordevice 560 can additionally be configured to have barriers 438-B1,438-B2, . . . 438-Bn that are altered in response to different levels ofelectrical stimuli and/or reservoirs 434-A1, 434-A2, . . . 434-An thathave different types and/or concentrations of monitor atoms and/ordifferent matrices or media in which monitor atoms are contained.

Thus, in the illustrated embodiment of FIGS. 56A/56B, in a similarmanner to the embodiments described above, different combinations of thereservoir, the barrier and the monitor region can be configured to beparticularly sensitive to different types, different magnitudes and/ordifferent durations of wear-out stresses.

Controlled initialization or activation of wear-out monitor devicesdescribed above with respect to FIGS. 43-56B can be implanted in contextof semiconductor packaging. The wire bonding technology is widely usedfor interconnecting integrated circuits to the outside word. In thefollowing, implementation of the controlled initialization of wear-outmonitor devices in the context of wire bonding is described.

FIG. 57 is an illustration of a wear-out monitor device 570 configuredto record an indication of wear out of a core circuit based on atomicdiffusion of monitor atoms that is localized within the wear-out monitordevice, according to embodiments. In particular, the wear-out monitordevice 570 includes a substrate 64, which can be an integrated circuit(IC) including metallization levels integrated therein. The wear-outmonitor device 570 includes one or more monitor regions D1, D2, . . . Dnformed in the substrate 64. The one or more monitor regions D1, D2, . .. Dn can be formed in or on, e.g., directly in or on the semiconductormaterial of the IC in some embodiments, or be formed over metallizationlevels of the IC in other embodiments. The wear-out monitor device 570additionally includes one or more barriers 438 formed on the one or moremonitor regions D1, D2, . . . Dn, and one or more wire bonds 572 formedon the one or more barriers 438 to serve as reservoirs 434. The one ormore barriers 438 can be formed of and configured in a manner similar tovarious embodiments described supra. In addition, the one or more wirebonds can be formed of and configured in a manner similar to variousembodiments described above and compatible with the wire bondingtechnology. In the monitor device 570, advantageously, the wire bonditself includes the monitor atoms and therefore serves as the reservoir434. Elements such as gold, silver, copper and platinum, for example,can serve as the monitor atoms as well as providing the electricalconnection to the IC.

In operation, a barrier 438 may be altered in any manner described aboveto initialize the diffusion of monitor atoms, in response to a wear-outstress, into a respective one of the monitor regions D1, D2, . . . Dn.Subsequently, when the monitor atoms diffuse into the a respective onthe monitor regions D1, D2, . . . Dn, and/or when atoms of therespective monitor region diffuse into the respective wire bond, theresistance across the wirebond-barrier-monitor region. Without beingbound to any theory, one mechanism that can cause a change in resistancecan arise from a phenomenon known as Kirkendall effect, which isassociated with interdiffusion of atoms giving rise to formation ofatomic vacancies and voiding over time.

FIG. 58 is an illustration of a wear-out monitor device 580 configuredto record an indication of wear out of a core circuit based on atomicdiffusion of monitor atoms that is localized within the wear-out monitordevice, according to embodiments. The monitor device 580 is similar tothe wear-out monitor device 570 described above with respect to FIG. 57except, different ones of the one or more wire bonds 582-1, 582-2, . . .582-n serving as the reservoirs 438 are formed of or incorporatedifferent monitor atoms, such as gold, silver, copper and platinum, toname a few. The description of other features of the wear-out monitordevice 580 that are similar to those of the wear-out monitor device 570illustrated above with respect to FIG. 57 is omitted herein. Thus, inthe illustrated embodiment of FIG. 58, in a similar manner to variousembodiments described above, different combinations of the reservoir,the barrier and the monitor region can be configured to be particularlysensitive to different types, different magnitudes and/or differentdurations of wear-out stresses.

FIG. 59 illustrates a cross-sectional view of a system 590, e.g., apackage-level or a board-level integrated system, including a pluralityof wear-out monitor devices 592A, 592B, 592C, where each wear-outmonitor device is configured to record an indication of wear out of acore circuit based on atomic diffusion of monitor atoms that islocalized within the wear-out monitor device, according to embodiments.In some implementations, the system 590 is an embedded system, wherevarious components are embedded within layers of a substrate (e.g., aPCB substrate) during the fabrication process. In particular, the crosssectional view shows a plurality of wear-out monitor devices 592A, 592B,592C that are embedded within respective layers of a substrate, whereeach monitor devices can be configured to monitor, among other things,temperature fluctuations and/or mission profiles of different layers (ornext/near to specific components) within the system 590.

Still referring to FIG. 59, the wear-out monitor devices 592A, 592B,592C can have various features configured differently for monitoringdifferent wear-out stresses and/or monitoring wear-out stresses atdifferent times. As illustrated, the wear-out monitor devices can beembedded or incorporated as part of a package-level integrated systemalong with other passive/discrete components and/or microprocessors thatinclude core circuits to be protected, according to embodiments. Inaddition, the wear-out monitor devices can be connected or linked to aco-ordinating ASIC and also links that could be modifiable (e.g., fusesthat could be blown or electrically modified), according to embodiments.

In various embodiments described above, wear-out monitor devicesconfigured to record an indication of wear out of a core circuit havebeen described in which a barrier can be altered by an electricalstimulus to initialize wear-out monitoring. However, embodiments are notso limited and in other embodiments, the barrier can be altered usingoptical energy. FIG. 60A illustrates a cross-sectional view of a system600, e.g., a package-level or a board-level integrated system includinga plurality of wear-out monitor devices 602A, 602B, where each wear-outmonitor device is configured to record an indication of wear out of acore circuit based on atomic diffusion of monitor atoms that islocalized within the wear-out monitor device, according to embodiments.Unlike the wear-out monitors described above with respect to FIGS.43-59, in which the barrier, when present, is configured to be alteredto initialize the wear-out monitor devices 600A, 600B in response to anelectrical stimulus, e.g., voltage or current pulses, which in turn maygenerate heat by Joule heating which causes the barrier to be altered,in the wear-out monitor devices 600A, 600B, the barrier is configured tobe modified in response to optical energy. The system 600 may includevarious other components, e.g., passive/active components, ASIC, etc.,as described above.

The illustrated package of the package-level system 590 is an organiclaminate-based package. However, embodiments are not so limited and thepackage can also be based on a ceramic material to protect the packagedcomponents. As illustrated, the various components may be embedded orcovered by the packaging material, e.g., an organic laminate material toprotect various components against moisture, etc. To allow opticalaccess of the barriers in the wear-out monitors, in some embodiments,optically transparent openings or apertures may be formed through thepassivating layer, and/or the insulating package of the wear-out devices600A, 600B when present. The openings or apertures may be sealed in someembodiments with a cap. In some other embodiments, the openings mayinclude an optically active cap, which can be configured as a lens, afilter or other optical components. When present, a filter canselectively pass desired wavelengths, and when present, a lens can focusthe light to provide an increased intensity of the light for causing alocal increase in temperature. In some other embodiments, the cap canalso be configured to protect the wear-out sensor.

Still referring to FIG. 60A, in some embodiments, the barrier is formedof a material that is directly altered by photons of light. For example,the barrier may be formed of an organic material, e.g., a polymericmaterial, which can be altered by photons. In other embodiments, thebarrier is formed of a material that is indirectly altered by light,e.g., by the heat generated by the light. The optical energy source thatcan alter the barrier can light sources, e.g., visible, infrared,ultraviolet and X-ray sources, including lasers, light emitting diodes,lamps, etc.

FIG. 60B illustrates a cross-sectional view of a system, e.g., apackage-level or a board-level integrated system 610 including aplurality wear-out monitor devices 612A, 612B integrated therein, whereeach wear-out monitor device is configured to record an indication ofwear out of a core circuit based on atomic diffusion of monitor atomsthat is localized within the wear-out monitor device, according toembodiments. The system 610 may be a pre-fabricated system similar tothe system 600 illustrated above with respect to FIG. 60, which includeswear-out monitors 602A, 602B. The system 610 may be configured to bemounted on another system 614. In embodiments, the system 614 caninclude various control and sensing circuitry to control and sense thewear-out monitor devices 612A, 612B, which can be implemented in anASIC. Advantageously, the illustrated configuration allows for acustomized/prefabricated system 610 including various embedded wear-outmonitor devices 612A, 612B to be coupled to the system 614 thatco-ordinate the various activities of the system 610.

Wear-Out Monitor Devices with Wear-Out Indication Based onInterdiffusion

In various embodiments of wear-out monitor devices described above,indications of wear-out of a core circuit are based on measuring anelectrical property associated with the effect of atomic diffusion ofmonitoring atoms into a monitoring region from a reservoir. For example,the reservoir may be a layer containing the monitor atoms that is formedon the surface of a substrate. The monitoring region may be, e.g., avolume of substrate material that serves as a diffusing medium for themonitoring atoms.

For some combinations of materials, when a first material is in contactwith a second material, atoms of the first material diffuse into thesecond material while atoms of the second material diffuse into thefirst material. This phenomenon is referred to as interdiffusion.According to various embodiments described herein, the monitoring regionand the reservoir of monitor atoms are configured such that the monitoratoms and the atoms of the monitoring region interdiffuse in response towear-out stresses. In these embodiments, the resulting compositionalchange in the reservoir can give rise to measurable electricalsignatures of the wear-out stresses. Thus, in the embodiments describedbelow, unlike the embodiments described above, the reservoir can beconsidered as the monitor region, and the substrate can be considered asthe source of the diffusant, or monitor atoms.

FIG. 61 illustrates how wear-out monitor devices can be configured suchthat an indication of wear-out of a core circuit based on interdiffusionof atoms can be utilized, according to embodiments. FIG. 61 illustratesthe wear-out monitor device 470 described above with respect to FIG. 47,which is configured to record an indication of wear out of a corecircuit based on atomic diffusion of monitor atoms that is localizedwithin the wear-out monitor device, according to embodiments. Asdescribed above, the wear-out monitor device 470 has one or morereservoirs of monitor atoms (i.e., first and/or second electrodes 408 a,408 b) disposed on a surface of the substrate and a monitor region(e.g., depletion region formed underneath the second heavily dopedregion 454 b) formed in the substrate 450. As described above, e.g.,with respect to FIG. 42A, one approach to quantifying wear-out of a corecircuit is to measure leakage current, e.g., reverse bias leakagecurrent across a PN junction, after exposure to wear-out stress atdifferent times. Thus, as illustrated in FIG. 42A, the increasingleakage current with increasing wear-out stress, e.g., thermal stress,can be used to quantify the wear-out of the core circuit.

A scanning electron microscope (SEM) image 614 illustrates anotherapproach of quantifying the wear-out. The SEM image 614 is arepresentative image of the first electrode 408 a serving as thereservoir formed of gold, after being subjected to a wear-out stressused to generate the experimental data illustrated with respect to FIG.42A. As illustrated in the SEM image 614, after being subjected tothermal wear out stress at 200° C. for 1-9 days, formation of silicondioxide on the first electrode 408 a serving as the reservoir of goldindicates that interdiffusion has occurred. That is, while diffusion ofgold from the gold electrode into the PN junction in the siliconsubstrate causes an increase in the reverse bias current, diffusion ofsilicon from the substrate into the gold electrode leads to formation ofsilicon oxide resulting from oxidation of silicon atoms that has reachedthe surface of the gold electrode.

FIG. 62A illustrates a cross-sectional view of a wear-out monitor device620 configured such that electrical signatures based on interdiffusionof atoms can be utilized, according to embodiments. The wear-out monitordevice 620 has formed on a substrate 64 one or more electrodes, e.g.,first reference electrode 622 and a second reference electrode 624, anda reservoir 434. Each of the first and second reference electrodes 622,624 are separated from the substrate 64 by a permanent diffusion barrier626. In some embodiments, the first and second reference electrodes 622,624 and the reservoir 434 initially have the same composition and/ordimensions comprising the monitor atoms. Furthermore, in someembodiments, the spacing between the first and second referenceelectrodes 622, 624 and the spacing between the second referenceelectrode 624 and the reservoir 434 initially have the same dimensions.

In operation, as described above with respect to FIG. 61, the reservoir434 and the substrate 64 have compositions such that, under a wear-outstress, e.g., a thermal stress, the monitor atoms in the reservoir 434and the atoms of the substrate 64 interdiffuse such that the monitoratoms diffuse into the substrate and the atoms of the substrate 64diffuse into the reservoir 434. In contrast, the presence of thepermanent diffusion barrier 626 prevents diffusion into and out of thefirst and second reference electrodes 622, 624 from and into thesubstrate 64. The interdiffusion between the substrate 64 and thereservoir 434 results in a change in the chemical composition of thereservoir 434, which in turn leads to changes in electricalcharacteristics of the reservoir 434, while the chemical composition andthe electrical characteristics of the first and second referenceelectrodes 622, 624 remain relatively unchanged. The electricalcharacteristics of the reservoir 434 that can change include theresistivity of the reservoir 434 and capacitances between the reservoir434 and other conductive structures, e.g., the second referenceelectrode 624.

As one illustrative example, when the reservoir 434 is formed of goldand the substrate 64 is formed of silicon, gold diffuses into thesubstrate 64 while silicon diffuses into the reservoir 434. As describedabove with respect to FIG. 61, inventors have found that theinterdiffusion results in a structural change in the reservoir 434,reservoir 434 and/or due to the formation of silicon oxide 628 on thereservoir 434. The structural change in turn leads to changes inelectrical property of the reservoir 434 that can be electricallymeasured using a sensing circuit.

FIG. 62B illustrates a close-up view of the wear-out monitor device 620illustrated in FIG. 62A electrically connected to a sensing circuit 629configured to detect electrical signatures associated with thestructural modifications to the reservoir 424 resulting frominterdiffusion of atoms, according to embodiments. One exampleelectrical signature of wear-out of a core circuit that can be measuredon the wear-out monitor device 620 using the sensing circuit 629 is theelectrical resistivity of the reservoir 424. The electrical resistivityof the reservoir 424 may increase, due to the presence of silicon atomsin the reservoir 424 and/or the formation of silicon oxide on thereservoir 424 as described above. Another example electrical signatureof wear-out of a core circuit that can be measured on the wear-outmonitor device 620 is the capacitance between the reservoir 434 servingas a first plate and another conductive structure serving as a secondplate of a capacitor. For example, the second reference electrode 624can serve as the second plate of the capacitor, whose capacitance valuemay change with exposure to wear-out stresses, e.g., thermal wear-outstresses. As the thickness of silicon oxide 628 in the gap between thesecond reference electrode 624 and the reservoir 434 increases, thecapacitance changes, e.g., increases, whose change can be quantitativelycorrelated to the aggregate wear-out stress that core circuit has beenexposed to. Furthermore, in embodiments where the first referenceelectrode 622 is included, the capacitance between the first and secondreference electrodes 622 and 624 can serve as a reference capacitancethat does not change or changes significantly less relative to thechange in capacitance between the second reference electrode 624 an thereservoir 434. Advantageously, because the changes in electricalproperties resulting from the diffusion of substrate atoms into thereservoir 434, the wear-out monitor device 624 does not rely onsemiconductor device structures such as PN junctions formed in thesubstrate 64.

FIGS. 63A-63D illustrate cross-sectional views of a wear-out monitordevice 630 configured such that electrical signatures based oninterdiffusion of atoms can be utilized to measure wear-out of a corecircuit, according to embodiments. The wear-out monitor device 630 isconfigured similarly to the wear-out monitor device 560 described abovewith respect to FIGS. 56A-56D, where the monitor regions 562-1, 562-2, .. . 562-n may be electrically connected to the sensing circuit 568described above with respect to FIG. 56D configured such that theelectrical properties of the monitor regions 562-1, 562-2, . . . 562-n,e.g., electrical resistance and/or capacitance associated with thereservoir 434, resulting from substrate atoms of the bulk substrate 64diffusing into the reservoir 434, can be individually measured.

In the wear-out monitor device 630, in addition to or in lieu of beingconnected to the monitor regions 562-1, 562-2, . . . 562-n, as describedabove with respect to FIGS. 56A-56D, the monitor device 630 is connectedto the reservoir 434 and configured to measure changes in electricalproperties of the reservoir 434 caused by diffusion of atoms of thesubstrate 64 into the reservoir 434, including resistance (FIG. 63B) andcapacitance (FIG. 63C/63D). Thus, unlike the sensing circuit 568described above with respect to FIGS. 56A-56D, the sensing circuits 632a-632 c illustrated with respect to FIGS. 63A-63D can measure thechanges in electrical properties of the reservoir 434 with or withoutelectrical connections to the monitor regions 562-1, 562-2, . . . 562-n,thereby providing an independent indication of wear-out of a corecircuit.

In addition, as illustrated in FIGS. 63A-63C, changes in electricalproperties of the reservoir 434, e.g., electrical resistance and/orcapacitance associated with the reservoir 434, can result from substrateatoms of the bulk substrate 64 diffusing into the reservoir 434.Additionally or alternatively, changes in electrical properties of thereservoir 434 can be caused by diffusing atoms from a seed materialformed on the surface of the reservoir 434.

FIG. 63B illustrates the wear-out monitor device 630 electricallyconnected to a sensing circuit 632 b configured to measure changes inthe electrical resistance associated with diffusion of atoms of thesubstrate 64 into the reservoir 434. The sensing circuit illustratedwith respect to FIG. 63B includes, for example, a voltage changedetection circuit, including an analog-to-digital converter (ADC) 635and a current supply 634, for detecting resistance changes associatedwith diffusion of the atoms of the substrate, e.g., silicon, into thereservoir 434, e.g., formed of gold, or with growth of silicon oxide onthe reservoir 434, as described above with respect to FIGS. 56A-56D.

FIG. 63C illustrates the wear-out monitor device 630 electricallyconnected to a sensing circuit 634 configured to measure changes incapacitance associated with formation of an oxide on the surface of thereservoir 434. The sensing circuit 634 illustrated with respect to FIG.63C includes, for example, instead of direct connection to the reservoir434, a gap electrode 636 having an initially predefined gap spacingbetween the gap electrode 636 and the surface of the reservoir 434.Referring to FIG. 63D, as the oxide on the surface of the reservoirincreases in thickness with increasing exposure to wear-out stresses asdescribed above with respect to FIGS. 56A-56D, the gap spacing continuesto reduce in proportion to the increasing oxide thickness. The resultingchanges in the capacitance between the gap electrode 636 and thereservoir 434 can be correlated to the wear-out stress.

Wear-Out Monitor Devices Configured for Time-Resolved Monitoring

As described with respect to various embodiments above, electricalproperties such as the leakage current, the resistance or thecapacitance of a monitor region can be used to obtain the concentrationof monitor atoms at certain locations of the monitor region. Theconcentration of the monitor atoms in turn can be indicative of adiffusion profile, which can be used to construct an integrated historyof the wear-out stress. In addition, as illustrated in FIG. 64A, basedon initial and final concentration profiles 640 of the monitor atomsbefore and after being subjected to a wear-out stress, informationrelated to a cumulative history of the wear-out stress, e.g., a constantthermal wear-out stress, as illustrated by a temperature time plot 642can be obtained. However, in various applications, as illustrated withrespect to FIG. 64B, the core circuit may be subjected to wear-outstresses whose magnitude varies over time, such as, e.g., a temperaturestress on the core circuit that varies over time, as illustrated by atemperature-time plot 646 and the resulting concentration profiles 644.In these applications, it may be desirable to configure a wear-outmonitor device such that the indication of time-variable wear-outstresses can be recorded.

To address this and other needs, according to various embodiments, awear-out monitor device is configured such that, after recording adiffusion profile in a monitor region in response to a wear-out stress,e.g., a thermal wear-out stress, the wear-out monitor device isconfigured to apply an electric field to the monitor region in a lateraldirection The monitor atoms diffused in the monitor region have a chargestate such that, when the electric field is applied to the monitorregion having the monitor atoms diffused therein, the electric fieldcauses the monitor atoms to further diffuse in monitor region thelateral direction. That is, a diffusion profile resulting from awear-out stress is laterally translated, in a manner analogous to aconveyor belt.

Measuring the average temperature is useful for estimating the workinglifetime of a device, but the averaging process by its very nature meansthat the peaks and troughs in the temperature profile are not recorded.It would be beneficial to be able to discern the temperature history ofa device with greater granularity as the periods of higher temperaturedo most damage. FIG. 65 is a schematic graph 650 illustrating varyingtemperature profiles as a function of time. As can be seen from thegraph, the temperature in this example varies between peaks of 180° C.to around 30° C., and over the time period averages about 110° C.,resulting in snapshots of concentration profiles 652 of the monitoratoms in the monitor region at different times t₁, t₂ and t₃.

However, if we could form a moving average as represented by the line12, then it would be possible to more accurately record the damagecaused by temperature extremes experienced by the device. This wouldallow the impact of the damaging high temperature to be evaluated moreaccurately.

Recording temperature as a function of time by an active circuit intomemory would of course be feasible for a powered device although thememory or processing capacities may be onerous for a device over a longperiod of time. However, if the device were unpowered or in an extremelylow power state then such a recording process would not work.

The inventor realized that the diffusion process could be coupled with asuitable monitor structure, sometimes referred to herein as a recordingstructure, such that the variation of temperature as a function of timecould be recorded in a device. Furthermore, such recordation could beachieved even if the device was unpowered or in a non-power consumingstate.

As described herein, recording a physical state of a componentrepresented by diffusion profiles of monitor atoms can occur regardlessof whether the wear-out monitor device, also referred to herein as thewear-out monitor sensor, and/or the monitor structure is powered.Electrically measuring the state can be performed, however, with powersupplied to the wear-out monitor device and/or the monitor structure. Inthis context, recording the physical state associated with diffusionprofiles is to be distinguished with recording digital information,e.g., in a memory device.

FIGS. 66A-66C are a cross sectional views of a temperature wear-outmonitor device 660 in accordance with a first embodiment of thisdisclosure. The temperature wear-out monitor device comprises a firstregion 1020 which is exposed to a suitable material, in this example asmall volume of gold 1022 which is in contact with an upper surface 1024of the first region 1020. The first region 1020 is in contact with asecond region 1030 which acts as a diffusion history memory capturingthe diffusion rate as a function of time. In use, the second region 1030is subjected to an electric field which may be an externally appliedelectric field or an intrinsic electric field resulting from gradedimpurity concentrations within the semiconductor material, much like theinternal potential difference created across a p-n junction. Theconceptual arrangement shown in FIGS. 66A/66B may be embodied in manydifferent ways. The regions 1020 and 1030 may be regions within asemiconductor. In use, the monitor atoms, sometimes referred to hereinas solute, will interact with the semiconductor to become either a donoror acceptor impurity. In the case of gold as monitor atoms/impurity, thegold becomes effectively charged by accepting an electron (lower energystate), and this electron cloud around the gold atom(s) is pulled by theelectric field. The electron cloud then pulls the gold atoms. This isknown as ambipolar motion.

FIG. 67 shows a variation on the structure of FIG. 66A where themetallic block of gold 1022 has been deposited over an insulating layerof silicon dioxide 1032 and the first region 1020 is formed by avertical interface between the block 1022 and a layer of semiconductormaterial 1030 also deposited also over the insulating layer 1032 andacting as the second region. The layer 1032 can be formed over asubstrate 1040. Further variations on this theme are possible.

In order to record the variation of temperature with respect to time,the material which has entered the silicon at region 1020 moves awayfrom that region and is stored in a memory structure. While region 30provides the memory for storing the material, moving the material, e.g.,diffused gold (in this example) from the region 1020 is provided byanother mechanism. This can be done by applying a potential across thedevice such that the gold drifts along the second region 1030 at a knownand controllable rate. The potential could be provided by an externalsource as shown in FIG. 68. Here a voltage source 1050 is connected toelectrodes 1052 and 1054. Electrode 1052 may, as shown, be proximate orin contact with the gold 1022. The electrode 1054 is placed remotelyfrom the first electrode 1052 such that the second region 1030 isinterposed between the electrodes 1052 and 1054. An insulating barrier,for example in the form of a silicon dioxide filled trench 1060 mayserve to inhibit current flow between the electrodes 1052 and 1054 suchthat substantially no energy is drawn from the voltage source 1050during the operation of the memory. Thus, the voltage source 1050 mightbe implemented by a capacitor which is given an initial charge duringthe manufacture and/or packaging of the temperature wear-out monitordevice with the expectation that the capacitor can hold a suitablevoltage over the working life of the circuit associated with thetemperature wear-out monitor device. The separation between theelectrodes 1052 and 1054 and/or the voltage provided by the voltagesource 1050 effects the E-field strength acting along the second portionof semiconductor 1030, and consequently changes the drift velocity ofthe gold therein and hence the time period over which the element 1030acts as a memory as well as the granularity or resolution within whichthe temperature may be resolved.

The drift velocity of the impurity (e.g. gold) is proportional to theE-field, and hence is proportional to V.

As a result, an arbitrary distance L along the region 1030 relates to atime period t_(L) from implantation at L=0, with

$\begin{matrix}{t_{L} = {K_{D}\frac{L}{V}}} & {{Eq}.\;\lbrack 2\rbrack}\end{matrix}$where K_(D) is a drift velocity coefficient.

FIG. 69 is a cross section of a temperature wear-out monitor deviceconstituting another embodiment of this disclosure. The temperaturewear-out monitor device in this embodiment can work without an externalvoltage source. As before, an E-field is applied to move the diffusednoble metal such as gold (or other non-noble metal monitor atoms) awayfrom the first region 1020, and at a rate which is known andpredictable. In this embodiment the E-field is provided by a gradeddoping profile within the second portion 1030. The second portion 1030may be doped to form an extended PN junction or the second portion 1030may be doped with a graded profile of a single polarity, i.e. N type orP type. The doping concentration of the one of the dopants isschematically illustrated in FIG. 69. For example, the concentration ofa donor impurity, such as phosphorous, may be relatively low near thefirst region 1020 and relatively high in a volume designated 1070 whichis distal from the first region 1020. By contrast, the concentration ofan acceptor impurity such as boron may be relatively low in the region1070 and relatively high in a region 1072 proximate the first region1020. FIG. 70A is a graph showing the doping concentration with the endclosest the first region 1020 having a doping concentration ofapproximately 10¹³ impurities per cm³ rising to approximately 10¹⁸impurities per cm³ in a stepwise fashion over a distance of 20 microns.Such a doping profile can be achieved by masking the surface of thesecond region and then etching apertures in the mask where theconcentration of apertures varies such that the mask is largely open orfully open at one end and mainly closed, i.e. with only a few apertures,at the other end, and which the aperture density varying there between.Once the mask is removed the substrate can be heat treated in order todiffuse the phosphorous away from the implantation sites in order tocreate a stepwise approximation to the linear graded profile which inturn gives rise to an electric fuel distribution as shown in FIG. 70Band a voltage potential across a device varying as a function ofdistance as shown in FIG. 70C.

FIG. 71 schematically illustrates how a “blob” of monitor atoms whichhas entered the second region 1030 progresses along the second region asa function of time under the influence of the electrostatic fields. Theconcentration of the diffused gold is shown over a plurality of snapshots T1 to T5 taken at different instances in time, for example onemonth apart, six months apart or one year apart as appropriate althoughlonger or shorter periods are also possible depending on the voltagegradient acting along the second portion 1030. Because the gold hasdiffused into the second portion 1030 by way of the first portion 1020,the gold has a varying density profile. For diagrammatic simplicity, thedensity of the gold is represented by shaded areas in the diagram. Area1080 represents a portion of a first high concentration and area 1082represents an region of a second (reduced) concentration an area 1083represents a third area of further reduced concentration. The E-fieldacts to migrate this region of material along the memory portion 1030,and in the diagram from left to right. Meanwhile, the gold will alsostill be subject to some diffusion. Thus the blocks 1080, 1082, and 1083translate from left to right due to the action of the E-field and spreaddue to the action of diffusion. Thus at time T2 region 1080 hastranslated to a new position and is now bounded on either side by aregion of reduced concentration 1082 and region of further reducedconcentration 1083.

By the time T3 is reached the region 80 has diffused so much that goldat first concentration no longer exists. The concentration has droppedinto the range represented by 1082 bounded by regions of reducedconcentration 1083 c and fourth (further reduced) concentration 1085. Bythe time T4 is reached concentration at the second level represented bya region 1082 no longer exists and instead we have region 1083 boundedby regions of the fourth concentration 1085, and regions of a fourthconcentration 1087 and a sixth concentration 1088.

By the time T5 is reached the block of impurity has diffused to becomebroader and is now comprised of regions of the fourth, fifth and sixthconcentrations. Thus it is to be noted that as the monitor atoms driftsfrom left to right as a function of the E-field, it also broadens as aresult of diffusion. FIG. 72 graphically represents the same informationas FIG. 71, but now showing diffusion profiles against nominal centerposition as time progresses from T1 to T6, for a region of contacthaving been made at time T0.

As noted before, the effective initial concentration is a function oftemperature and the actual doping concentration noted in the wear-outmonitor device after a period of time can be regarded as a convolutionof the various monitor atom concentrations as a result of changes intemperature at the interface between the gold and the semiconductor.

Having successfully demonstrated mechanisms for encoding the prevailingtemperature into a spatially modulated doping profile within a portionof semiconductor which acts as both a wear-out monitor device and amemory, there is a need to be able to address and read data from thememory.

FIG. 73 is a cross section to a first embodiment of an array readdevices where a plurality of electrodes 1100, 1102, 1104, 1106 and 1108are formed in a spaced apart manner within the second region 30 of thesemiconductor. Although only five electrodes have been shown, fewer ormore may be provided. In order to avoid setting up a Schottky barrier,each one of the electrodes 1100 to 1108 may be deposited over a smallhighly doped region 1100 a to 1108 a.

Each of the electrodes may be selected by a multiplexer, or each pair ofelectrodes may be selected by a multiplexer, to place it in contact witha measurement circuit such that a leakage current between adjacentelectrodes can be measured or a leakage current between any selected oneof the electrodes 1100 to 1108 and a further electrode or semiconductorregion formed beneath the layer 1030 or to one side of the layer 1030can also be determined.

FIG. 74 shows the arrangement of FIG. 73 in a plan view.

FIG. 75 is a cross section through the device along the line A-A′ ofFIG. 73, where the second region 1030 has been doped to be an N-typeregion (either with or without a graded doping profile depending onwhether the device is intended to be able to operate in an unpoweredmode). The second region 1030 is formed as an elongate finger within aP-type well 1110. A contact 1112 is made to the P-type material 1110 byway of a highly doped region 1113. The surface of the semiconductor iscovered by a passivation layer 1115, for example silicon dioxide, exceptwhere the contacts 1112 and 1116 are formed. The well may be bounded (ifdesired) by further doped regions so as to form reverse biased p-njunctions or as shown in FIG. 75 by insulating walls as is known insilicon on insulator fabrication techniques.

In a further embodiment, as shown in FIG. 76, a plurality of transistorsmay be formed spatially along the length of the second region 1030. Inthis illustration transistors 1120, 1122, 1124, 1126, 1128, 1130, 1132,1134, 1136, 1138, 1140, 1142, 1144, 1146, 1148, 1150, 1152, 1154, 1156and 1158 are formed such that one of their active regions, for exampletheir drains, are positioned on one side of the region semiconductor1030 and another of their active regions, for example their sources, arepositioned on the other side of the region 1030. The wear-out monitordevice may be formed in a variety of sizes depending on the desiredtemporal resolution and period of use. Without limitation wear-outmonitor devices may range from tens of microns to hundreds of microns inlength.

The transistor construction may be that of a JFET or a MOSFET orsimilar. In a JFET construction the drain-source doping may extendbeneath the second region 1030, and the second region may act as a gate.In a MOSFET construction the second region may be of the samesemiconductor type as the drain and source regions so as to form achannel between the drain and source, and a further electrode may beprovided over the second region 1030. In other embodiments thesemiconductor around and including the second region 1030 may be dopedso as to form bipolar junction transistors where the region 1030 may,for example, form an elongate base. Emitter regions may be providedadjacent or within selected portions of the region 1030 and contacts maybe made to the emitter regions. A further implant adjacent the region1030 can act as a collector. The collector region may be shared by thebipolar junction transistors or each transistor may be fabricated withits own collector.

During a reading, a reference voltage can be applied to the secondregion 1030, and then parameters of the transistors 1120 to 1158 may bedetermined, the parameters being a function of the doping in a channelportion for each one of the respective transistors. Parameters mayinclude pinch-off voltage, leakage, gain, frequency response and so on.

Each of these parameters can be read but will actually also be avariable as a function of temperature of the die at the time the data isread on the devices. It is therefore desirable to include a further readstructure which is positioned such that it cannot be influenced bydiffusion of the monitor atoms. This can be achieved either by placingthe read structure at the distal end of the second region 1030 at such adistance that diffusion of the monitor atoms is unlikely within theworking lifetime of the device, within a region where the drift fieldinhibits monitor atoms interfering with the operation of the referencedevice or by fabricating the reference device in an isolated region ofthe semiconductor.

There may be instances where it is desired to modify the ability of thedopant material, e.g. gold, to diffuse into the semiconductor. Forexample, it may be desirable to inhibit diffusion if a temperature isbelow a first threshold where the results are largely relevant, or abovea second temperature range where the gold diffuses too fast. Under suchcircumstances, it might be desired to use further wear-out monitordevices with further different doping materials.

For example, if it is desired to measure over a high temperature range,then an impurity or monitor atoms with a higher activation energy shouldbe chosen. Silver has an activation energy in silicon of 1.6 eV makingit suitable for use at higher temperatures.

For monitoring at temperatures of many hundreds of degrees platinum withan activation energy of 2.2 eV or aluminum with an activation energy of3 eV may be suitable.

For lower temperatures, copper with an activation energy of 1.0 eV orsodium with an activation energy of 0.76 eV may be used. This list isnot exhaustive and is given only by way of example.

FIG. 77 schematically illustrates a wear-out monitor device arrangementwhere the dopant 1022 is held on a cantilever 1200. The cantilever maybe formed by adjacent layers of dissimilar materials having dissimilarcoefficients of thermal expansion. Thus the cantilever acts like abi-metallic strip, tending to bend in one direction as it warms and inanother direction as it cools. The choice of direction of bend is at thedesigner's discretion. Thus, the dopant material 1022 may be held awayfrom the temperature wear-out monitor device during a first range oftemperatures and forced into contact with the first region 1020 of thetemperature wear-out monitor device over a second range of temperature.The contact can either be made as the temperature increases if theuppermost layer 1202 expands more than the lowermost layer 1204; or itmay be lifted away as the temperature increases if the lowermost layer1204 has a higher temperature coefficient of thermal expansion as thelayer 1202. This, in conjunction with the electric field sweeping thedopant along the array, allows a more binary approach to temperaturesensing to be adopted, with relatively high concentrations of the dopantindicating that the strip support the dopant 1022 into contact with thesurface, and relatively low concentrations indicating that the dopant1022 had been pulled away from contact with the surface of thesemiconductor.

In some instances it may desired to inhibit recording or enablerecording temperature after certain events, for example after firstpower up. Such an arrangement may be achieved by using a structuresimilar to that shown in FIG. 77 where the dopant 1222 is carried on amovable cantilever on an electrically controlled microelectronicmechanical system. Such MEMS systems, for example switches, are wellknown to the person skilled in the art.

For example, in the arrangement shown in FIG. 78, the cantilever may benaturally biased such that it contacts the dopant 1022 with thesemiconductor material in the first region 1020. However, this contactcan be broken by applying a voltage to the control electrode 1210 on anopposing side of the teeter-totter arrangement shown in FIG. 78, therebylifting the dopant 1022 out of contact with the first region 1020. Thusthe provision of a suitable voltage on the control contact 1210 may beused to pull the dopant 1022 out of contact with the first region 1020.Similarly, if a control electrode is formed on the other side of theswitch opposing the electrode 1210, then the electrodes could be used topull the dopant into contact with the region 1020.

Other mechanisms to move the block of monitor atom material 1022 intoand/or out of contact with the semiconductor may also be used. Forexample mechanical force acting across a membrane exposed on one side toa fluid may be used to form a pressure wear-out monitor device to recordover-pressure or under-pressure events. Furthermore if the contactfootprint is profiled such that the contact area varies with pressurethen the magnitude of the over-pressure event may be encoded within themonitor atom concentration.

FIG. 79 schematically illustrates a data retrieval circuit which may beembedded on a die with the temperature wear-out monitor device describedhereinbefore. A multiplexer 1250 is provided to select one of theplurality of inputs 1260.1 to 1260.n which interact with the readstructure. Thus, if the read structure is formed as a plurality of diodelike structures then the inputs 1260.1 to 1260.n select individual onesof the electrodes 844 shown in FIG. 84. If, however, the read structureis formed of the transistors, then the inputs 1260.1 to 1260.n canselect between individual ones of the transistors 1120 to 1158 shown inFIG. 76. An output of the multiplexer is provided to a first input of adifference amplifier 1270. A second input of a difference amplifier 1270receives a reference signal from the reference signal generator 1280.The reference signal generator 1280 may be formed by an identical readdevice as used in the temperature wear-out monitor device, but where asource of the monitor atoms is not provided. The reference device 1280is used to compensate for the temperature effects on the read circuit atthe time of taking a reading. The difference signal output by theamplifier 1270 is digitized by a digital to analog converter 1290 andprovided to a data processor 1300. The data processor 1300 may beimplemented by a programmable data processor. Alternatively, it may beimplemented as a combination of a state machine that controls themultiplexer 1250 and a lookup table in order to translate the outputvoltage per concentration. The data processor 1300 provides an output1302. The output 1302 may be provided by way of a contacting or wirelesscommunications link at the designer's choice. Other circuitconfigurations are possible, such as configuring the measurementcomponents into Wheatstone bridge like circuits.

The circuits described herein may be implemented on a functional die.Alternatively, the circuits disclosed herein may be provided on aspecialized die 1320 which is co-packaged with a die containing afunctional circuit 1322 within a chip scale package 1324 asschematically illustrated in FIG. 80.

The arrangements described so far have been appropriate to a temperaturewear-out monitor device. However, given that the rate of diffusion isalso a function of concentration, then the teachings disclosed hereincan also be applied to a concentration monitor.

FIG. 81 schematically illustrates a plan view of a concentration monitorin accordance with the teachings of the present disclosure. Theconcentration monitor, generally designated 1330 and shown in a planview comprises two or three channels. A first channel 1332 that can beincluded is a temperature reference channel. A second channel 1334 thatcan be included is a temperature measurement channel and a third channel1336 that can be included is a concentration measurement channel. Thesecond channel 1334 is formed from one of the embodiments describedhereinbefore. The first channel 1332 is similarly formed, but does notinclude the source of monitor atoms 1022. The concentration channel 1336is formed much like the temperature channel 1334, but instead the gold1022 is not applied and an aperture 1360 is formed such that secondmonitor atoms, or reagent, whose concentration has been measured candiffuse into the first region of the third channel 1336. Each of thechannels includes measurement structures of the type describedhereinbefore and is connected to a suitable data processing circuit. Thetemperature channel 1334 can be similar to the temperature wear-outmonitor devices described with respect to various embodiments, e.g.,with respect to FIGS. 66A/66B, and can include a first region and asecond region, where the first region is adapted to be exposed to firstmonitor atoms and the second region is adapted to migrate the firstmonitor atoms away from the first region. When included, the temperaturereference channel 1332 includes a third region corresponding to thesecond region of temperature channel 1334. When included, theconcentration measurement channel 1336 includes a third region includingthe aperture 1360 to expose the second monitor atoms or reagent and afourth region in contact with the third region and adapted to migratethe second monitor atoms or reagent along the fourth region.

In the arrangements shown and described hereinbefore the wear-outmonitor device keeps a permanent record of the temperatureconcentration. This is achieved by causing the impurity atoms to driftfrom the impurity source along the body of the wear-out monitor deviceunder the influence of an intrinsic electric field, or a built-inelectric field, or of an externally applied electric field. The electricfield is applied along a first direction. The provision of an electricfield may also be used to periodically clear the wear-out monitor deviceby sweeping the impurity atoms away from the read structure. Such anarrangement is schematically illustrated in FIG. 82, where a source ofmonitor atoms 1022 and the read structure, designated 1380, are formedat the surface of a region of semiconductor 1400. In use, the monitoratoms is swept through the semiconductor in an X direction by anintrinsic electric field set up by the doping, or as shown here bypotential difference V1 applied between electrodes 1410 and 1412.However, from time to time, a second voltage V2 applied betweenelectrodes 1420 and 1422 may be used to sweep the impurity atoms in theY direction. If V2 is much greater than V1 then it can be seen that theread structure 1380 can effectively be reset by applying the secondvoltage V2 to sweep the impurity atoms out of the measurement/readregion 1380.

FIG. 83 illustrates a wear-out monitor device 840 configured fortime-resolved monitoring of wear-out of a core circuit, according toembodiments. The illustrated device structure is similar to thosedescribed supra. It will be appreciated that a graph of depletion widthversus dopant concentration such as the one illustrated can be utilizedto tailor the relative width (depth) and/or sensitivity of the depletionregion as a monitor region.

FIG. 84 illustrates a wear-out monitor device 840 configured fortime-resolved monitoring of wear-out of a core circuit, according toembodiments. The illustrated device 840 includes a plurality of PNjunctions regions in vertical and lateral directions, where one of the Pregions has formed thereon a reservoir of diffusant or monitor atoms,and each of the P and N regions has formed thereon an electrode 844. Asconfigured, the plurality of contacts allow an electrical property,e.g., leakage current, associated with the quantity of diffuseddiffusant atoms to be recorded as a function of vertical and/orhorizontal position, which can in turn indicate a temporal history. Inaddition, as discussed in more detail below, by utilizing diffusantatoms that have a charge, the electrodes can be utilized to “fastforward” or “rewind” the movement of the diffusant atoms.

FIG. 85 illustrates a plurality of wear-out monitors, in which differentones of the wear-out monitor devices can be enabled and co-ordinatedusing a combination of different features described above, depending onthe application. The wear-out monitors in FIG. 85 have barrier layersformed between the reservoir of monitor atoms and the underlyingsubstrate. As illustrated and described supra, individual wear-outmonitors can be initialized at different times by applying a stimulus,e.g., a voltage, to alter or eliminate the barrier layer of theindividual wear-out monitor devices, thereby initializing the wear-outmonitor devices. Wear-out monitor devices that are initialized are readyto diffuse the monitor atoms from the reservoirs into the substrate, andchanges in electrical properties resulting therefrom can be measured.

FIG. 86 illustrates a plurality of wear-out monitors arranges in anarray, where accessing individual diffusion monitor devices can beco-ordinated by fuses. For example after a certain time period/operatinglife of a first wear-out monitor device D1, a first fuse F1 connected tothe first wear-out monitor D1 may be blown, and subsequently a voltageis applied to a second wear-out monitor device D2 such that D2 is nowthe active monitor. Using an application specific multiplexing systemthe different inputs/outputs (I1 . . . In) can be co-ordinated (suchthat fuse blowing may not be desired) and electrical outputs effectivelyshowing relative differences in the diffusion of the atoms from thedifferent monitors may provide valuable information.

FIGS. 87-94 illustrate embodiments of a wear-out monitor device having aplurality of wear-out monitor devices or regions (e.g., D1, D2, . . . )electrically connected to sensing circuitry configured for monitoring,e.g., time-resolved monitoring, of wear-out of a core circuit, accordingto embodiments.

FIG. 87 illustrates an arrangement of wear-out monitors comprising aplurality of wear-out monitors or regions (D1, D2, . . . Dn) eachconnected to a transistor and a sensing circuitry for time-resolvedmonitoring, according to embodiments.

FIG. 88 illustrates a wear-out monitor (cross sectional view on theleft, plan view on the right) comprising a plurality of reservoirs 434each comprising the monitor atoms that are separated from a substrate 62by a barrier 438, according to embodiments. Similar to the wear-outdevice illustrated with respect to FIG. 43A, each of the reservoirscontain monitor atoms, e.g., Au, and each of the barriers 438 is formedof a material that can be eliminated or consumed when a sufficientelectrical stimulus, e.g., voltage or current, is applied to initiatediffusion of the monitor atoms. Each of the barriers 438 can beconnected to a transistor to provide the electrical stimulus. Asillustrated in the plan view, the barrier 438 is configured as a thinfilm in areas where the reservoir or monitor atoms are disposed, suchthat high current applied to the barrier 438 forms an opening in thebarrier 438 by, e.g., melting or electromigration, to initiate thediffusion.

FIGS. 89-94 illustrate wear-out monitors comprising a substrate (e.g.,Si) having formed thereon a reservoir of monitor atoms (e.g., Au) and aplurality of electrodes (D1, D2, . . . Dn) for time-resolved monitoring,according to embodiments. As described elsewhere, each of D1, D2, . . .Dn may be formed on a PN junction formed in the substrate, in which thedepletion region can serve as a monitor region.

FIG. 89 illustrates a substrate is connected to a “fast forward” and/ora “rewind” circuitry and configured to laterally diffuse the monitoratoms towards left or right by flowing current in the left or rightdirections depending on the charge state of the monitor atoms, once themonitor atoms have diffused into the substrate from the reservoir.

FIG. 90 illustrates the electrodes being connected to a reverse biasleakage multiplexed measurement circuitry, according to embodiments. Inone implementation, when a positive is applied to an n+ region, e.g.,+1V, the diode would be under a reverse bias would force about 0V onboth positive and negative terminals.

FIG. 91 illustrates the electrodes being connected to a reverse biasleakage multiplexed measurement circuitry comprising a referencestructure for differential measurements, according to embodiments.

FIG. 92 illustrates a plurality of monitor MOS transistors T1, T2, . . .TN whose gates serve as the electrodes D1, D2, . . . Dn . . . Themonitor MOS transistors as well as a reference transistor are connectedto a differential amplifier for a differential measurement, according toembodiments. The circuitry is configured to measure, among otherparameters, shifts in the MOS threshold voltages while the MOStransistors are turned on, whose shifts may result from diffusion ofmonitor atoms into the channels of the MOS transistors. In operation,when the threshold voltages of the MOS transistors shift, the voltage atthe detection node changes accordingly. The measurement can be singleended or differential.

FIG. 93 illustrates a plurality of monitor MOS transistors T1, T2, . . .TN whose gates serve as the electrodes D1, D2, . . . Dn . . . Themonitor MOS transistors are connected to current sources. The circuitryis configured to measure, among other parameters, leakage currentthrough the channels while the MOS transistors are turned off. Inoperation, after the detection nodes are initially pulled high by thecurrent sources, current leakage through the channels resulting frommonitor atoms that may have diffused therein pulls the detection nodelow.

FIG. 94 illustrates a sensing circuit configured to measure reverse biasrecovery current. The electrodes are configured to receive controlsignals for driving the diodes from forward to reverse bias by theinverter/buffer. When the diode is driven from forward to reverse bias,the voltage at the left of Rin is pulled approximately to GND. Becauseof the diode reverse recovery, the voltage at the left of Rin is pulledbelow GND. This signal is amplified and converted to measure the diodereverse recovery.

FIG. 95A illustrates a sensing circuit 950 configured to measure reversebias recovery current comprising a monitor diode 952 and configured formonitoring wear-out of a core circuit, according to embodiments. It hasbeen recognized that when switching from a conducting to a blockingstate, a diode or a rectifier has stored charge that must first bedischarged before the diode blocks reverse current. This discharge takesa finite amount of time known as the reverse recovery rime, or t_(rr).During this time, diode current may flow in the reverse direction. Theinventors have discovered that the reverse recovery time (t_(rr)) ofsuch a diode is altered by impurities, e.g., gold, entering the PNjunction of the diode as a result of wear-out stress. Based on thiseffect, the wear-out of the core circuit can be semi-quantitativelydetermined, according to embodiments. The illustrated circuit 950 isconfigured to switch the monitor the diode 952 from a forward biasedconfiguration to a reverse biased configuration, and to measure thereverse recovery therefrom, to semi-quantitatively determine the amount,the type and/or the location of the impurities resulting from thewear-out stress.

FIG. 95B illustrates current and voltages measured at different nodes ofthe sensing circuit 950 illustrated in FIG. 96A, as the monitor diode952 is switched from a forward biased configuration to a reverse biasedconfiguration. Illustrated four graphs from the top of page correspondsto a voltage at the inverter output which provides the switching voltageV_(diode) across the diode 952, current I_(diode) across the diode 952,voltage V_(sense) across the sense resistor R_(sense) serially connectedto the diode 952 and the output voltage V_(out) across the amplifier, asa function of time. As illustrated, the second graph from the top ofpage illustrates the current measured across the diode 952 as ittransitions across different regions, including a forward bias region, aforward recovery region and a reverse bias region. A positive voltageoutput from an amplifier can be used to semi-quantitatively determinethe wear-out of the core circuit.

FIG. 96A illustrates a reference circuit 960 comprising a referencediode 962, which does not have impurities diffused therein. Thereference circuit 960 includes various circuit components thatcorresponds to the circuit components of the sensing circuit 950illustrated above with respect to FIG. 95A, except, instead of themonitor diode 952 configured to monitor wear-out of a core circuit, thereference circuit 960 includes the reference diode 962. The referencediode 962 does not, for example, include monitor atoms that areconfigured to diffuse into the depletion region of the diode 962.

FIG. 96B illustrates current and voltages measured at different nodes ofthe reference circuit 960 illustrated in FIG. 96A, as the referencediode 962 is switched from a forward biased configuration to a reversebiased configuration. The four graphs illustrated in FIG. 96Bcorresponds to the four graphs illustrated with respect to the sensingcircuit 950 in FIG. 95B. In particular, the second graph illustratescurrent across the reference diode 962 of FIG. 96A as it is switchedfrom a forward biased configuration to a reverse biased configuration,using the sensing circuit 960 illustrated in FIG. 96A. As illustrated, arelatively smaller voltage output from an amplifier compared to thevoltage output measured in FIG. 95B can be used as a reference tosemi-quantitatively determine the wear-out of the core circuit.

Wear-Out Monitor Devices Configured for Reversing the DiffusionDirection of Monitor Atoms

As described with respect to various embodiments above, theconcentration of monitor atoms at certain location within a wear-outmonitor device can be indicative of an integrated history of a wear-outstress. Because atomic diffusion can be driven by concentrationgradient, without an opposing chemical potential, the net movementdirection of the monitor atoms tends to be in the direction ofdecreasing concentration of the monitor atoms. As a result, for variousconfigurations, the wear-out monitor device can be configured as“one-time use” devices. However, for some applications, it may bedesirable to be able to “rewind” the movement of monitor atoms in areverse direction after being subjected to a wear-out stress.

To address these and other needs, similar to various embodimentsdescribed above, a wear-out monitor device is configured such that thewear-out stress causes the monitor atoms to diffuse away from thereservoir and into the monitor region. Furthermore, the wear-out monitordevice is configured such that the monitor atoms are adapted to have acharge state when diffused in the monitor region, and configured toapply an electric field to the monitor region such that, when theelectric field is applied to the monitor region having the monitor atomsdiffused therein, the electric field causes the monitor atoms to diffuseaway from the monitor region and back into the reservoir. It will beappreciated that the direction of movement of the monitor atoms in theseembodiments is in a direction of increasing concentration gradient.Thus, according to various embodiments, the wear-out monitor device isconfigured to apply the electric field having a magnitude such that,when the electric field is applied to the monitor region having themonitor atoms diffused therein, the electric field causes the monitoratoms to diffuse in the direction of increasing concentration gradient.These embodiments are described with respect to FIGS. 97 and 98.

FIG. 97 illustrates a cross-sectional view of a wear-out monitor device,similar to those illustrated with respect to FIGS. 56A and 63A, inoperation, where the wear-out monitor device is configured such thatelectrical signatures based on interdiffusion of atoms can be utilizedto measure wear-out of a core circuit, according to embodiments. FIG. 98illustrates a cross-sectional view of the wear-out monitor device ofFIG. 97 and a control and sensing circuitry connected to the device. Inparticular, the devices illustrated in FIGS. 97 and 98 comprise aplurality of regions, where each region is configured to be initializedusing an external stimulus, and for monitoring, e.g., time-resolvedmonitoring, of wear-out of a core circuit, according to embodiments.After being initialized and being subjected to wear-out stress therebyallowing the monitor atoms to diffuse into respective monitor regions,because the monitor atoms are adapted to have a charge state whendiffused in the monitor regions, by applying an electric field to themonitor regions having the monitor atoms diffused therein, the monitoratoms are caused to diffuse away from the monitor region and back intothe reservoir.

Sensor Network Systems Based on Wear-Out Monitor Devices Configured forControlled Initialization, for Time-Resolved Monitoring and forReversing the Diffusion Direction of Monitor Atoms

Some devices include a core circuit that has a predicted time and/or apredicted amount of usage that can lead to failure of the core circuit.The predicted time-to-fail and/or the predicted usage-to-fail aresometimes calculated and/or experimentally determined for a set ofconditions, e.g., average conditions. For example, a mean time tofailure may be calculated for electromigration-related failures can bebased on a set of conditions including current density, temperature andactivation energy. However, the actual time and/or usage of the corecircuit are sometimes significantly different (e.g., below or above)from the time and/or usage conditions under which the failure ispredicted, leading to unexpected failure or unnecessary replacement.Thus, there is a need to alert a user of the core circuit of anindication of wear-out that more closely represents the actual time orusage the core circuit has been subjected to. In the following, systemsintegrating various embodiments of the wear-out monitors & missionprofile monitors are described, to address this and/or other needs.

According to various embodiments, a sensor network system includes asensor node network. The sensor node network includes a plurality ofsensor nodes, where each of the sensor nodes includes one or morewear-out monitor devices described above and an application processingunit. The one or more wear-out monitor devices are separated from andsuitably arranged relative to a core circuit, and are configured torecord an indication of wear-out of the core circuit, wherein theindication is associated with localized diffusion of a diffusant withinthe wear-out monitor device in response to a wear-out stress that causesthe wear-out of the core circuit. The wear-out monitor devices areconfigured to record an indication of wear-out regardless of whether thewear-out monitor device of the sensor node is powered or unpowered. Thesensor node network is communicatively coupled to a server or a hostedservice to transmit the recorded indication thereto. The server or thehosted service is configured to communicate the indication of wear-outto a user and/or to provide an alarm signal indicating to replace apart.

There are many different application-specific systems that can bedeployed with the wear-out monitors disclosed herein. In reference toFIG. 99, a system, e.g., a sensor network system for monitoring wear-outof a core circuit, is described.

The illustrated system of FIG. 99 includes one or more sensors.According to embodiments, the sensors may be arranged in a sensor node1450. As described herein, one or more sensors arranged in a module maybe referred to as a sensor node. In various embodiments, a sensor node1450 can include one or more sensors configured for capturing data,e.g., in an unpowered package. The sensor node can additionally includean application processing unit (APU), which in turn includes one or moremicroprocessors, RAM, nonvolatile RAM (NVRAM), a hard disk,communications modules and/or a collection of physical interfaces. Asensor node additionally has one or more data access interfaces toenable the collection of captured data. These interfaces include, butare not limited to, GPIO pins, USB ports, parallel interfaces, RS232connections, Ethernet ports or a radio for wireless transmission (RF,Wi-Fi, Bluetooth, etc.), among other ports or interfaces. As usedherein, data that has been collected from a node via physical orwireless means is known as a data stream while in transit.

Installation and configuration of a sensor node can be performed, e.g.,over a secured protocol to ensure the node can be securely and safelyadded to the sensor network. This ensures that all nodes can be trustedin a network and prevents unauthorized nodes from gaining access to thenetwork.

Still referring to FIG. 99, data recordings or readings can be capturedat each sensor node. In some applications, depending on the environmentand data processing capabilities of a sensor node, data can betransformed into information at each sensor node. Information includesdata that has been transformed using analytic data processing algorithmsto determine enhanced or greater resolution of the data been captured.In some applications, depending on the network environment andprocessing capabilities of a sensor node, captured data can be securedusing encryption or similar methods to prevent unauthorized access.

Still referring to FIG. 99, data/information captured at the one or morenodes is transferred or transmitted (depending on the capabilities ofthe sensor node) to an upstream system 1454. As described herein, anupstream system is a separate, independent piece of equipment that isnot a sensor node but configured to store, process and make availableall the data and/or information from a sensor network. The upstreamsystem secures the data, depending on the capabilities of the sensornode, network environment and application needs of the system. Theupstream system transforms the data into information, whose informationcan be used to address specific domain problems encountered by theapplication covered by the system.

Still referring FIG. 99, the sensor node of the illustrated system canhave various configurations according to embodiments, as describedbelow.

In some embodiments, the sensor node is configured under a zero powermode. In this mode, the sensor is configured to take readings and tostore the readings without having to read from or store the readings tonon-volatile random access memory (NVRAM), or with the continuousapplication of power.

In this mode, a microprocessor (MP) or NVRAM modules can be omitted. Aninterface can be provided to enable on-demand reading of each sensornode.

In some embodiments, the sensor node is configured under a continuousoperation mode. In this mode, the sensors are continuously powered (e.g.via mains supply or battery), and is configured to take continuousreadings from each sensor at a predetermined time interval. Thesereadings are stored in NVRAM and can be later communicated to upstreamsystems using one or more interfaces.

In some embodiments the sensor node is configured under a mode in whichthe sensors are configured to be periodically waken up and to recordlatest readings. Under this mode, using an internal clock (via crystalor other), some NVRAM and some simple logic circuits the system areperiodically waken-up from an ultra-low powered, deep sleep state andreadings are taken from each sensor the readings are stored in NVRAM.These readings can be later communicated to upstream systems using oneor more interfaces.

In some embodiments, the sensor node is configured under a mode in whichthe sensors are configured to be waken up to an interrupt event and torecord latest readings. Under this mode, with the addition of a MP andsome I/O circuits, the system could wake up to an interrupt event andtake a reading from each sensor and store those readings in NVRAM. Thesereadings can be later communicated to upstream systems using one or moreinterfaces.

For the various sensor node configurations, the NVRAM can be configuredsuch that when NVRAM is approaching capacity, the sensor node can beconfigured to either stop recording readings or use a first in first out(FIFO) methodology to continuously record the readings.

For various sensor node configurations described above, the sensor nodecan be configured to sense instantaneous node operating conditions inaddition to the one or more sensor readings, to analyze the data usingon-board algorithm processors to perform computations for makinginformed decisions about the data, and to store the results of thesecomputations (i.e. store information not data). For example, thisinformation could be used in additional computations to refine theperiod of wakeup or configuration of interrupt controllers to betterutilize power capacity or to ensure a critical event is captured.

The sensors and sensor nodes may be further arranged in a sensornetwork. As described herein, a collection of sensor nodes may bereferred to as a sensor network. A sensor network can cover, e.g., asingle piece of equipment, a room, building, facility or geographicregion including the entire planet. In the following, variousconfigurations of a sensor network is describe, according toembodiments.

FIG. 100 illustrates a sensor network 1501 is communicatively coupled toa an upstream system including a private server 1509 through a networktransmission 1502. The network and upstream systems are private to thebusiness/organization and information gathered from transforming thecaptured data in the sensor network is used for applications specific tothat business/organization.

The data captured from the network can be secured at each node usingencryption or similar and securely transmitted to the private server.All network transmission, over either physical or wireless medium can beperformed securely. The data transmission can be secured using aprotocol that ensures confidentiality (the data stream cannot be accessby unauthorized persons), integrity (ensuring that the data streamcannot be tampered with or changed) and utilizing authentication (toensure that we identify that users and/or systems are who they claim tobe).

Examples of secured transmission protocols include secure sockets layer(SSL), hashed message authentication codes (HMAC) and public/private keyexchange.

The upstream server includes a system controller 1504 that routes andseparates command and control (CnC) instructions from datacollection/processing instructions. CnC instructions include but are notlimited to network configuration commands, new node installation/setupcommands and network health management.

CnC instructions are routed to a node manager 1506. A node is configuredto process and to handle all CnC instructions.

Data collection and processing instructions are routed to a processingengine 1505. The processing engine 1505 is configured to store data asappropriate, transform data into information using data analyticalalgorithms, store information as appropriate and raise events dependingon the system application needs, configuration and the results of thedata transformation into information.

An event manager 1510 is configured to handle all raised events in thesystem. Event handling can include but is not limited to user displayupdates, email notifications, upstream system interactions and sensornetwork CnC instructions (e.g. forced shutdown command).

All data and information is persisted to a backing store. A backingstore can include but is not limited to data files or databases 1508(both relational and non-relational). The data is stored utilizing adata schema. An example schema that includes a sensor node and datadatabase tables are illustrated below with respect to TABLES 2 and 3below.

TABLE 2 Nodes Table Unique id for the node Application type or functionof the node Geolocation details for the node if appropriateSalts/encryption keys used to decrypt data and communicate with the node

TABLE 3 Data Table The unique node identifier that captured the readingThe value captured Timestamp of when the readings where transmitted orcollected from the node Depending on the node geolocation details on thenode when the data was captured

FIG. 101 illustrates a sensor network communicatively coupled to cloudhosted services, according to embodiments. Sensor network data can becollected and transmitted to a hosted service or services, sometimesreferred to as cloud computing services. The cloud is configured topersist, analyze and transform the data into information and take actionappropriate action on that information.

These hosted services can be private (a private network within abusiness or facility), hybrid (a combination of public internetaccessible services and a private networks) or public (internetaccessible services) depending on the application needs and sensornetwork deployment.

Example of a public cloud is where the hosted services are used tocapture data from a range of customer's privately owned sensor networks.The cloud utilizes its scale and processing capabilities to inferanomalies or significant information from the transformed data that isof value to each customer.

Possible service deployments include but are not limited to thefollowing models.

A software-as-a-service (SaaS) model where the software and algorithmsare sold to customers who are free to deploy these services on thehosted service network of their choice.

A platform-as-a-service (PaaS) model where each customer retainsownership and control of their data but online hosted services areprovided and made available for the storage and analysis of their data.

Still referring to FIG. 101, the cloud, hosted services utilize a loadbalancer 1501 to ensure and efficient distribution of sensor networkdata streams to upstream processing systems. The distribution isgenerally but not exclusively based on volume and current load ofbackend hosted system.

FIG. 102 illustrates a sensor network according to embodiments, in whichthe sensors are configured to collect data by communicating directlywith a private server or hosted services. However, a more practicalapproach is to use a proxy server to collect the data/informationreadings from the sensor network and is responsible for transmittingthat collected data to upstream systems.

In the illustrated embodiment of FIG. 102, a proxy server can utilizesecured protocols to transmit the data streams to upstream systems.

In general, a proxy server 1605 can have high capacity storage availableto collect and store the data from the sensor network. Depending on thecapacity and real time criticality of captured data the proxy server canbe configured with an appropriate interval for communicating the data toupstream systems.

Under some circumstances, a proxy server can utilize a short rangewireless protocol 1604 (e.g., Bluetooth) to collect data from the sensornetwork.

Under some circumstances, each sensor node could be directly connectedto the proxy server utilizing a physical connection 1603 (e.g., RS232)and data could be transmitted over this connection.

A sneakernet device 1612 can be used to collect the data from each nodeand upload to the proxy server. A sneakernet refers to the transfer ofelectronic information by physically moving storage media (e.g. USBflash drives) or a reader device with on board storage from the sourceto the destination rather than transmitting the information over a wiredor wireless network.

Without limitation, according to various embodiments, integrated circuitdevices comprising one or more wear-out monitor devices/sensors (WOS)that can be configured to be used as part of a sensor network systemdescribed herein include one or more of the following features.

As described above, WOSs can record a wear-out state regardless ofwhether the WOs be powered or un-powered, and can be activated byvarious wear-out stresses including pressure, gas, time, voltage and/orcurrent. A system combines the status of the WOSs and enables a higherlevel system take decisions of the combined status. The WOS can bederived to vary are different rates or in the presence of acurrent/voltage etc.

The WOS can be enabled or disabled by use of a physical “gatematerial/substance”.

The WOS can be implemented through the monitoring of two physicalphenomena that occur due to the presence of a primarymaterial/structure/sensor (e.g. Gold, diffuses into silicon crystallattice and then free silicon atoms oxidize on the upper surface of thegold, both physical phenomena can be electrically measured andcontrolled)

The WOS can be implemented using one or more realizations to create moredata points on the current state of the device under monitoring.

The WOS may be created using multiple layers of material or primarymaterial plus another element/substance to enable the monitoring ofmultiple temperature ranges by a single sensor.

The current state of the WOS can be reversed/reset/cleared undercontrol.

The physical implementation of the WOS can enable unique signatures tobe read from the WOS on a device per device basis.

The physical implementation of the WOS can enable atom counting.

The physical implementation of the WOS can allow for the enabling ordisabling of some or all connectivity to the WOS through physicalchanges to the material boundaries

The physical implementation of the WOS can enable multiple read pointsfor a single/multiple source element/material.

A WOS could be used to detect that a device/chip/module has only beensoldered once

A barrier material may be used around/about/in-way-off to control thenormal spread of the solvent/solute.

The barrier can/may be for blowing to enable (electrical, photonic,chemical, physical stress, breakdown, decay, etc.), for non-blowing toenable, for evaporation to enable.

The WOS can enable an additional capacitor differential sensor throughphysical growth of material e.g. silicon dioxide. This would allow thesingle sensor to generate two separate data point on wear out.

In some embodiments, one or more WOSs are embedded in the package for asingle/multiple die, including SOCs and SIPs.

In some embodiments, one or more WOSs are contained within the samephysical module and or 3D-printed assembly. Examples of physical moduleinclude a PCB board or flexible-substrate with multiple integratedcircuits, but could equally be a system with or without physicalconnections between each component, example a ribbon cable, flex, RF andor optical.

In these embodiments, the WOS can be electrically and physicallyintegrated to be inside a physical module. In other embodiments, the WOScan be electrically integrated but physically disposed external to thephysical module. When external to the physical module, the WOS cancapture ambient conditions.

In addition, the module can be active or passive. When the module ispassive, the module has no independent power source but is capable ofbeing read by an external device with its own power. When the module isactive, the WOS is configured to monitor when, e.g., only when,power/voltage/current is present.

In some embodiments, WOSs can be embedded in a 3D-printed structure,where interconnect is embedded into/on-to the 3D-printed structure. Thisapproach can enable multiple WOSs to be distributed throughout astructure.

In some embodiments, one or more WOSs are encapsulated in amodule/structure that will experience extreme environmental conditions,e.g., temperature ranges. In these embodiments, relatively moresensitive electronics are kept at a suitable distance away or isolatedfrom the source of the extreme environmental conditions, e.g.,temperature sources. The WOSs can be connected via a physical/optical/RFmedium that enables the ability to take a reading from the sensor.

In some embodiments, one or more WOSs are stored in a module with theminimum electronics for remotely and/or wirelessly transmitting sensorreadings either on demand or periodically.

Periodic data transfer can be made either through a powered sensor, orthrough harvested environmental energy (light, sun, temperature).

The remote module/structure can also be polled through RFID waves. Someremote communication methods can use a secure protocol.

The WOSs could be used as a “service life” meter, where after a giventime the WOS flags to the system that the device has reached it maximumlife and flags for replacement. This “service life” could be active orpassive and could be for time, temperature, pressure, voltage, current,gas, etc.

FIG. 103 illustrates various physical and electrical connections thatcan be made to various wear-out monitor devices described supra, forintegration into a sensor network system, according to embodiments. Inparticular, the illustrated wear-out monitor device is similar to thedevice illustrated with respect to FIG. 98. In particular, theillustrated devices comprises a plurality of regions, where each regionis configured to be initialized using an external stimulus, and formonitoring, e.g., time-resolved monitoring, of wear-out of a corecircuit, according to embodiments.

Examples of Sensor Network Systems Based on Wear-Out Monitor DevicesExample: System A

The inventors have recognized that it can be difficult to determine theactive lifespan of a part comprising a core circuit when the part sitson a shelf in an inactive state for a relatively very long time. Knowinghow long a part sat inactive before been used can be useful in failureanalysis and general characterization of a part's lifetime performanceand capability.

To address these and other needs, a sensor network system based onwear-out monitor devices according to embodiments is illustrated withrespect to FIG. 1. In reference to FIG. 104, using multiple WOSs wherebyone or more are based on materials that diffuse at room temperature wecan take a reading when the part is first powered on and note that if aWOS shows a high level of diffusion then we know that the part has satinactive for a long time before it was used. This is logged tonon-volatile memory (NVM) or other persistent storage and can be used inprecision analog circuit trimming and or post failure diagnostics,characterization or even to warn/indicate to the user the remaininglifetime and capabilities of the part. One or more of the sensors couldbe active.

A suitable cloud platform (cloud infrastructure that includes security,data processing and management technologies, across standardcommunication infrastructure) can be used to assist in failurediagnostics and or preventative-maintenance. As part of the sensormodule registration process, significant attributes of the module suchas unique-identifying-code, unique-identifying-profile of the WOS,diffusion levels of the WOS, can be recorded and reported on; andcompared to the standard diffusion profile for the given device/moduleapplication space. This process could be available to users orrestricted to a manufacturer's failure analysis organizations or aroyalty based system protection division.

Once the sensor/module is registered, the manufacturer can provide anadditional cloud service to help customers determine the operatingconditions of the part, and expected lifetime remaining. For example anautomotive device could flag final operation in xweeks/days/hours/minutes, giving the user a period of time to replacethe device before it disables itself.

Thus, the System A can advantageously capture near full life history ofa core circuit in a part during use, from calibration to failureanalysis.

Example: System B

The inventors have recognized that the performance or accuracy of a WOScan be dependent on the material and operating temperature range of thepart. It would be useful to capture and correlate out of bandtemperature events, for example, temperature spikes for a brief momentor long exposure to a temperature range below the activation level ofthe WOS material.

To address these and other needs, a system according to embodimentsbased on wear-out monitor devices include a combination of passive (WOS)and active sensors. Using the combination, additional readings can bemade while the part is powered. These reading can be used in conjunctionwith the WOS reading to determine a more complete temperature profile ofthe system. In conjunction with a wake-up timer an actual profile couldbe captured and stored in NVM or communicated for external processing ina supervisor system and or a cloud infrastructure.

Thus, the System B can advantageously provide accurate temperatureprofile logging at a device level.

Example: System C

The inventors have recognized that data degradation can occur due tocosmic rays or particles, which can have serious consequences forsystems that depend on non-ECC memory storage.

To address these and other needs, a system according to embodimentsinclude memory chips with a WOS and detect a cosmic particle collisionevent due to a unique diffusion signature. This event could then beacted on by the system to either reset the system to a known good stateor used a post failure analysis logging event.

The device registration process includes a system check to determine theinitial state of the WOS and will flag any such events. Subsequent datasynchronizations to the cloud servers can include a check for sameevents.

Thus, the System C can advantageously detect radiation-induced error(RIE).

Example: System D

The inventors have recognized that, it can be advantageous to detectdie-cloning and or tampering and or other unauthorized access to adevice and its internal system code.

To address these and other needs, a sensor network according toembodiments include a WOS configured to generate a unique source ofentropy with a predictable diffusion progression based on the standardmission profile for the device. The system algorithm can detect if anattempt is made to inject a foreign decryption key to unlock system codeor that a physical/electrical event (e.g. removing the cap of adevice—large heat spike) has occurred that might indicate that someoneis attempting to gain unauthorized access to the device. Thisinformation can be used to ‘brick’ the device or otherwise attempt toput the IP sensitive parts of the device beyond the reach of theattacker.

The combination of intrusion sensors and “bricking” a device can be asolution for IoT applications and embedded hardware solutions, ashacking organizations invest significant resources in gatheringinformation on the device or devices they wish to attack. When possible,the hackers physically obtain target devices they wish to hack andattempt to reverse engineer the device and use it to test possibleattacks.

Flagging potential hacks sometimes does not result in shutting off thedevice. In such applications where forcing a module shutdown can resultin severe consequences (personnel health, machine health, securitybreaches), the preferred approach is to log an alert with the cloudplatform. The cloud administrators can remotely deactivate the device.

Communicating with a hosted service, e.g., a cloud hosted service, canbe through a variety of mechanisms, as described in FIGS. 105 and 106:

For more advanced triage purposes, geo-location hardware and monitoringcan establish if the module was in the expected operating location, asdescribed in FIG. 106:

Such use of technology can also be applied to internal failure analysis,where expensive processes and resources can be replaced by analyzing thecloud data. There is potential to sell this “intrusion detection” moduleand cloud service to customers with more expensive hardware or where itis preferred to conduct failure analysis in situ.

Thus, the System D can advantageously detect intrusions and protectdevice/customer IP.

Example: System E

The inventors have recognized that it can be advantageous to secure IoTmodules in the cloud.

To address this and other needs, a system is configured such that, atany given time, the WOS records a unique diffusion amount and undernormal operation the value can be within operating bands or rates ofchange. This value can be used to generate cryptographically signed codeat boot time and algorithms can determine if firmware has been altereddue to reverse engineering, de-soldering etc. More advanced solutionscan combine the intrusion monitor with geo-location positioning.

Securing traffic to and from the device can be increased through aninitial registration process with the cloud where intrusion moduleparameters are recorded. Future communications will include thesevariables as a salt for encrypting the channel. In effect, there will bea way to securely communicate with each module through its own diffusionfingerprint.

Thus, the System E can advantageously be configured such that deviceencryption becomes non-operational if operating life specifications areexceeded.

Example: System F

The inventors have recognized that some devices are provided bymanufacturers with generic lifetime specifications. However, for thesedevices, no information may be available regarding how the customersutilize the devices and all returns are treated “equally” as we have noinformation on if the device reached its full lifetime. Thus, there is aneed to provide information regarding how the customers have used a parthaving a core circuit before the part has reached its full lifetime.

To address this and other needs, a sensor network system according toembodiments comprise a WOS or combination of multiple WOSs and activelife sensors, where the WOS(s) indicate specific operating lifetimes fora product. Once the lifetimes have exceeded, the device can becomeinoperable/shutdown. This could be invaluable for markets where qualityof service (QOS) is a high priority, e.g., in automotive/industrialapplications. The device could communicate it status (time to end oflife) to a supervisor system or external to the likes of the cloud,creating a replacement device revenue stream and a cloud monitoringrevenue stream.

CONCLUSION

In the embodiments described above, apparatus, systems, and methods forwear-out monitors are described in connection with particularembodiments. It will be understood, however, that the principles andadvantages of the embodiments can be used for any other systems,apparatus, or methods with a need for monitoring wear-out. In theforegoing, it will be appreciated that any feature of any one of theembodiments can be combined and/or substituted with any other feature ofany other one of the embodiments.

Aspects of this disclosure can be implemented in various electronicdevices. Examples of the electronic devices can include, but are notlimited to, consumer electronic products, parts of the consumerelectronic products, electronic test equipment, cellular communicationsinfrastructure such as a base station, etc. Examples of the electronicdevices can include, but are not limited to, a mobile phone such as asmart phone, a wearable computing device such as a smart watch or an earpiece, a telephone, a television, a computer monitor, a computer, amodem, a hand-held computer, a laptop computer, a tablet computer, apersonal digital assistant (PDA), a microwave, a refrigerator, avehicular electronics system such as an automotive electronics system, astereo system, a DVD player, a CD player, a digital music player such asan MP3 player, a radio, a camcorder, a camera such as a digital camera,a portable memory chip, a washer, a dryer, a washer/dryer, peripheraldevice, a clock, etc. Further, the electronic devices can includeunfinished products.

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,”“include,” “including” and the like are to be construed in an inclusivesense, as opposed to an exclusive or exhaustive sense; that is to say,in the sense of “including, but not limited to.” The word “coupled”, asgenerally used herein, refers to two or more elements that may be eitherdirectly connected, or connected by way of one or more intermediateelements. Likewise, the word “connected”, as generally used herein,refers to two or more elements that may be either directly connected, orconnected by way of one or more intermediate elements. Additionally, thewords “herein,” “above,” “below,” “infra,” “supra,” and words of similarimport, when used in this application, shall refer to this applicationas a whole and not to any particular portions of this application. Wherethe context permits, words in the above Detailed Description using thesingular or plural number may also include the plural or singularnumber, respectively. The word “or” in reference to a list of two ormore items, that word covers all of the following interpretations of theword: any of the items in the list, all of the items in the list, andany combination of the items in the list.

Moreover, conditional language used herein, such as, among others,“can,” “could,” “might,” “may,” “e.g.,” “for example,” “such as” and thelike, unless specifically stated otherwise, or otherwise understoodwithin the context as used, is generally intended to convey that certainembodiments include, while other embodiments do not include, certainfeatures, elements and/or states. Thus, such conditional language is notgenerally intended to imply that features, elements and/or states are inany way required for one or more embodiments or whether these features,elements and/or states are included or are to be performed in anyparticular embodiment.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the disclosure. Indeed, the novel apparatus, methods, andsystems described herein may be embodied in a variety of other forms;furthermore, various omissions, substitutions and changes in the form ofthe methods and systems described herein may be made without departingfrom the spirit of the disclosure. For example, while blocks arepresented in a given arrangement, alternative embodiments may performsimilar functionalities with different components and/or circuittopologies, and some blocks may be deleted, moved, added, subdivided,combined, and/or modified. Each of these blocks may be implemented in avariety of different ways. Any suitable combination of the elements andacts of the various embodiments described above can be combined toprovide further embodiments. The various features and processesdescribed above may be implemented independently of one another, or maybe combined in various ways. All suitable combinations andsubcombinations of features of this disclosure are intended to fallwithin the scope of this disclosure.

What is claimed is:
 1. An integrated circuit device comprising awear-out monitor device configured to record an indication of wear-outof a core circuit separated from the wear-out monitor device, thewear-out monitor device comprising a reservoir and a diffusion region,wherein the indication is associated with localized diffusion of adiffusant from the reservoir into the diffusion region in response to awear-out stress that causes the wear-out of the core circuit.
 2. Theintegrated circuit device of claim 1, wherein the reservoir is formed ata surface of a substrate, wherein the reservoir serves as a firstelectrode of the wear-out monitor device, and wherein the wear-outmonitor device further comprises a second electrode formed at thesurface and formed of a material different from the reservoir.
 3. Theintegrated circuit device of claim 1, wherein the diffusant has adiffusion activation energy between 0.75 eV and 2.5 eV.
 4. Theintegrated circuit device of claim 1, wherein the diffusant includes oneor more elements selected from the group consisting of aluminum (Al),cobalt (Co), platinum (Pt), sulfur (S), nickel (Ni), silver (Ag), zinc(Zn), gold (Au), chromium (Cr), copper (Cu), iron (Fe), sodium (Na), andpotassium (K).
 5. The integrated circuit device of claim 1, furthercomprising a sensing circuit electrically connected to the wear-outmonitor device and configured to detect an electrical property thatchanges in response to the localized diffusion of the diffusant.
 6. Theintegrated circuit device of claim 1, further comprising a controlcircuit configured to apply a stimulus to activate the wear-out monitorprior to recording the indication of wear-out.
 7. The integrated circuitdevice of claim 6, further comprising a physical barrier having anenergy barrier for diffusion of the diffusant disposed between thereservoir and the diffusion region, wherein the physical barrier isconfigured such that the energy barrier is reduced in response to thestimulus to activate the wear-out monitor device.
 8. The integratedcircuit device of claim 1, wherein the wear-out monitor device comprisesa plurality of monitor structures each configured to record anindication of wear-out of the core circuit.
 9. The integrated circuitdevice of claim 8, wherein different ones of the monitor structures areconfigured to be activated by different stimuli prior to recordingindications of wear-out of the core circuit.
 10. The integrated circuitdevice of claim 1, wherein atoms of a substrate serve as the diffusant,such that the wear-out stress causes atoms of the substrate to diffusefrom the substrate into a diffusion region in response to the wear-outstress.
 11. The integrated circuit device of claim 1, wherein thewear-out monitor device is configured to apply an electric field to adiffusion region in a first direction, and wherein the diffusant has acharge state when diffused in the diffusion region such that, when theelectric field is applied to the diffusion region having the diffusantdiffused therein, the electric field causes the diffusant to furtherdiffuse in the diffusion region in the first direction.
 12. Theintegrated circuit device of claim 11, wherein the diffusion region andthe reservoir are adjacently disposed in a second direction differentthan the first direction and configured such that the wear-out stresscauses the diffusant to diffuse in the second direction.
 13. Theintegrated circuit device of claim 12, wherein a plurality of conductivestructures are formed on a surface of the diffusion region along thefirst direction and provide electrical access to the diffusion region ata plurality of locations.
 14. The integrated circuit device of claim 1,wherein the wear-out monitor device is configured such that the wear-outstress causes the diffusant to diffuse away from the reservoir and intothe diffusion region, wherein the diffusant has a charge state whendiffused into the diffusion region, and wherein the wear-out monitordevice is further configured to apply an electric field to the diffusionregion such that, when the electric field is applied to the diffusionregion having the diffusant diffused therein, the electric field causesthe diffusant to diffuse toward the reservoir.
 15. The integratedcircuit device of claim 14, wherein the wear-out monitor device isconfigured to apply the electric field having a magnitude such that,when the electric field is applied to the diffusion region having thediffusant diffused therein, the electric field causes the diffusant todiffuse in a direction of increasing concentration gradient.
 16. Theintegrated circuit device of claim 1, wherein the wear-out monitordevice comprises a PN junction, and wherein the reservoir contacts oneof a p-doped region or an n-doped region of the PN junction.
 17. Theintegrated circuit device of claim 16, wherein the reservoir serves asan electrical contact for the one of the p-doped region or the n-dopedregion of the PN junction.
 18. A method of monitoring wear-out of a corecircuit of an integrated circuit device using a wear-out monitor deviceseparated from the core circuit, the wear-out monitor device comprisinga reservoir and a diffusion region, the method comprising: recording anindication of wear-out of the core circuit, wherein the indication isassociated with localized diffusion of a diffusant from the reservoirinto the diffusion region within the wear-out monitor device in responseto a wear-out stress that causes the wear-out of the core circuit;detecting a property that changes in response to the localized diffusionof the diffusant; and reporting the property of the wear-out monitordevice.
 19. The method of claim 18, further comprising, prior to therecording, activating the wear-out monitor device by applying a stimulusto overcome an energy barrier.
 20. The method of claim 18, furthercomprising applying an electric field to a diffusion region having thediffusant diffused therein to change a direction of diffusion of thediffusant in the diffusion region.
 21. The method of claim 18, furthercomprising, prior to recording, subjecting the wear-out monitor deviceto the wear-out stress that causes the localized diffusion of thediffusant from the reservoir into the diffusion region.
 22. The methodof claim 21, further comprising, prior to subjecting the wear-outmonitor device to the wear-out stress, activating the monitor device byapplying a stimulus to overcome an energy barrier.
 23. The method ofclaim 22, wherein applying the stimulus alters a physical barrier havingthe energy barrier and reduces the energy barrier.
 24. The method ofclaim 21, further comprising, after subjecting the wear-out monitordevice to the wear-out stress, applying an electric field to thediffusion region having the diffusant diffused therein in a firstdirection such that the electric field causes the diffusant to furtherdiffuse in the first direction.
 25. The method of claim 21, furthercomprising, after subjecting the wear-out monitor device to the wear-outstress which causes the diffusant to diffuse away from the reservoir andinto the diffusion region, applying an electric field to the diffusionregion having the diffusant diffused therein, such that the electricfield causes the diffusant to diffuse toward the reservoir.
 26. Anintegrated circuit device with wear-out monitoring of a core circuit inthe integrated circuit device, the integrated circuit device comprising:means for recording an indication of wear-out of a core circuit, thecore circuit separated from the means for recording, the means forrecording comprising a reservoir and a diffusion region, wherein theindication is associated with localized diffusion of a diffusant fromthe reservoir into the diffusion region within the means for recordingin response to a wear-out stress that causes the wear-out of the corecircuit; and means for detecting the indication of wear-out of the corecircuit, the means for detecting the indication of wear-out being incommunication with the means for recording the indication of wear-out.27. The integrated circuit device of claim 1, wherein the wear-outmonitor device comprises a semiconductor substrate.
 28. The integratedcircuit device of claim 1, wherein the wear-out monitor device comprisesan insulating substrate.
 29. The integrated circuit device of claim 1,wherein the wear-out monitor device and the core circuit are integratedin a common substrate.
 30. The integrated circuit device of claim 1,wherein the diffusant has a diffusion activation energy less than 3.0eV.
 31. The integrated circuit device of claim 26, wherein the means forrecording is configured to be activated in response to a stimulus priorto causing the diffusant to diffuse from the reservoir into thediffusion region.
 32. The integrated circuit device of claim 26, furthercomprising means for applying an electric field to the diffusion regionin a first direction, and wherein the diffusant has a charge state whendiffused in the diffusing region such that, when the electric field isapplied to the diffusing region, the electric field causes the diffusantto further diffuse in the diffusing region in the first direction. 33.The integrated circuit device of claim 26, wherein the means forrecording is configured such that the wear-out stress causes thediffusant to diffuse away from the reservoir and into the diffusionregion, wherein the diffusant has a charge state when diffused into thediffusion region, and wherein the recording means is further configuredto apply an electric field to the diffusion region such that, when theelectric field is applied to the diffusion region, the electric fieldcauses the diffusant to diffuse toward the reservoir.
 34. The integratedcircuit device of claim 26, wherein the reservoir is formed at a surfaceof a substrate, wherein the reservoir serves as a first electrode of themeans for recording the indication of wear-out, and wherein the meansfor recording the indication of wear-out further comprises a secondelectrode formed at the surface and formed of a material different fromthe reservoir.
 35. The integrated circuit device of claim 26, whereinthe diffusant has a diffusion activation energy between 0.75 eV and 2.5eV.
 36. The integrated circuit device of claim 26, wherein atoms of asubstrate serve as the diffusant, such that the wear-out stress causesatoms of the substrate to diffuse from the substrate into a diffusionregion in response to the wear-out stress.
 37. An integrated circuitdevice comprising a wear-out monitor device configured to record anindication of wear-out of a core circuit separated from the wear-outmonitor device based on diffusion of a charged diffusant, wherein thewear-out monitor device comprises: a reservoir comprising the chargeddiffusant; and a diffusion region in communication with the reservoirsuch that the wear-out stress causes the charged diffusant to diffusefrom the reservoir into the diffusion region.
 38. The integrated circuitdevice of claim 37, wherein the wear-out monitor device is configured toapply an electric field to the charged diffusant.
 39. The integratedcircuit device of claim 38, wherein the wear-out monitor device isconfigured to cause a change in a direction of diffusion of the chargeddiffusant by applying the electric field.
 40. The integrated circuitdevice of claim 38, wherein the charged diffusant has a charge sign andthe direction of the electric field is such that, upon application ofthe electric field, the charged diffusant diffuses in a direction ofincreasing concentration gradient of the charged diffusant.
 41. Theintegrated circuit device of claim 38, wherein the wear-out monitordevice comprises a PN junction and is configured to record theindication of wear-out based on localized diffusion of the chargeddiffusant in the PN junction.
 42. The integrated circuit device of claim38, wherein the wear-out monitor device further comprises a plurality ofelectrodes positioned at different distances from the reservoir, whereinthe electrodes are configured to apply the electric field.
 43. Theintegrated circuit device of claim 37, wherein the wear-out monitordevice is configured to initiate the diffusion of the charged diffusantupon activation by a stimulus prior to recording the indication ofwear-out.